This is a simple renaming without adaptation.

Commit c06f0f3a352 changed the base navbar zindex.
But the navbar of the translation mode still had old zindex values making the
navbar invisible, in fact under the base navbar.

task-1804662

* blog, gengo, sale

The variables.less file was producing CSS which was then multiplicated
by the number of bundles (see less_helpers).

Also simplify some LESS.

* website_sale

* web, website, mass_mailing

Before this commit, the editor allowed defining the margin of some
elements and the height of some elements. There were three main
problems with this system:

1) When an user dragged the arrow, he often expected to change the
   size of the element while he was in fact changing the margin

2) When changing the margin, you increase the space between two
   elements but with a white space (while most users want a space
   with the same color of the block they are resizing = padding)

3) When changing the height, the user was able to hide snippet parts
   and the height was not consistent accross screen sizes

Now, the only thing you can edit is padding. There is only one arrow
for each direction, which allows increasing spacing and consistent
dimension at the same time.
The only feature that is lost with this change is the ability to
control vertical alignement of colored columns. This is not a problem
as colored columns are rare in our current snippets and there still
have the possibility to add margin classes by hand if necessary (there
are also plans to control vertical alignement another way).

Note: margin classes are kept for compatibility.

Open customize options menus to the left if there is not enough space on
the right.

* mass_mailing, payment, point_of_sale, portal, survey, web, web_tour,
  website_blog, website_crm_partner_assign, website_event,
  website_event_questions, website_form, website_forum, website_gengo,
  website_hr_recruitment, website_links, website_mail,
  website_mail_channel, website_mass_mailing, website_quote,
  website_sale, website_sale_options, website_slides, website_twitter

This commit reviews the whole "JS side" of the web_editor and website
apps. This is a first step to be able to improve them with new and
better functionnalities; this commit is not supposed to change any
visual behavior.

The main goal was to achieve a structure similar to the backend one.
Now, the frontend side also has a root widget (like the WebClient)
and all other widgets are attached to it one way or another. This allows
the benefits of using the 'trigger_up' functionnality for example.

As RPC are now mainly done with the `this._rpc` functionnality (being
possible thanks to the parent hierarchy), the frontend will also be
possible to test thanks to QUnit in a future update (besides the "text"
editor side which still requires a refactoring to be able to do that).

---

Here are some of the changes:

(-) conventions and documentation

The code has been updated to follow JS conventions and a lot of code has
been commented (around +2000 lines of comment). This also means that
lots of functions have been renamed to use camelCase or simply to make
their name understandable.
See https://github.com/odoo/odoo/wiki/Javascript-coding-guidelines.

(-) deprecated: web_editor.base

The "web_editor.base" module has been split and does not force the
modules which require it to wait for DOM ready anymore. This was indeed
slowing loading times, but also prevented to use some modules in some
contexts (see the LESS editor use in web_studio which is the subject of
another task).
Now the "editor context" can be got thanks to the "web_editor.context"
JS module with its "get" function.
The "web_editor.base" module should probably not be used anymore (see
its code and recent updates).

(-) new: web.dom_ready

If a JS module should wait for the DOM to be ready to be executed, a
new JS module has been created: "web.dom_ready". This should always
be used in a module which only want to instantiate stuff. Do not
extend (or worst, include) classes after DOM ready.

(-) website.website

The "website.website" module has been split. "website.website" does not
return anything useful anymore, it just initialize some miscellaneous
stuff, without waiting for the DOM to be ready. You might want to check
"website.utils", "website.content.compatibility" or `WebsiteRoot`. Also
`website.form` has been deleted (use `this._rpc`), so has been
`website.error`. `website.prompt` will be removed in a future update to
be replaced by `Dialog.prompt`.

(-) widgets are great

Many classes which were not widgets are now widgets. This allows them to
use the 'events', the 'xmlDependencies' and the 'this._rpc' features for
example. Here are some of the main ones:

- Snippet options: these were classes with a `$el` for the menu element
    and `$target` for the customized element. This is still the case
    but following standard `Widget` structure (one exception: using
    `this.$(...)` searches in the `$target` as before this update).

- Snippet animations: instead of class instances with a `$target`
    element which can be `start` and `stop`, these are now standard
    widgets which can be `start` and `destroy`. `this.$target` is
    an alias to `this.$el` for ease of compatibility.

- Snippet editors: instead of class instances in charge of an editor
    overlay, these are now widgets. Each "child" snippet editor is
    properly attached as a "child", which allows editors to communicate
    and to be properly destroyed.

(-) root widgets and website navbar

The frontend is different of the backend. In the backend, the page has
an empty <body/> element and all the components are instantiated from
parent to children (i.e. the `WebClient` is instantiated and is in
charge of instantiating the `ControlPanel`, etc). The frontend cannot
work like that on page loadings as they are way more frequent than in
the backend and we do not want them to flicker. A frontend page is
loaded as a <body/> element which already contains the website navbar
and its menus and the whole content page. JS code has to be "attached"
to these existing elements. This is possible thanks to the `RootWidget`
instances and the specialized `WebsiteRoot`, `IframeRoot` and
`WebsiteNavbar` (see code for details).

(-) lazy loading

No more (or at least a lot less) XML/JS has to be loaded on page
loading, thanks to the use of the `Widget.xmlDependencies` feature.
XML which have to be lazy loaded is loaded only on related Widget
instantiation if necessary, which allows to execute a lot of JS code
before the DOM is ready and to start many widgets on DOM ready (not
later). A visual benefit of this is clicking on the 'edit' button as
soon as it is possible: before this commit, this was sometimes not
doing anything as event handlers were not binded yet.

Still a possible exception: loading the session and locales. This may
be asynchronous stuff which is still required before widget
instantiations but this will be the subject of another task.

(-) deprecated code and code location

More than reviewing code and organizing it, many apparent dead code was
removed. More importantly, mislocated code was put in the right app.
This is the case for snippet animations which is a concept for website
apps but was defined in the web_editor app, or some translation concepts
which were part of website but should have been part of web_editor.

---

There are probably more things to say about this commit but I will let
the comments speak for those.