This commit introduce a full redesign of all JS views.  We started
basically from scratch.  The goal was to unify all the various views
under a common framework, to make them testable, to make then usable in
different conditions (in studio, or in the frontend), and to make our
lives easier.

Some important points are:
- we introduced new coding guidelines (camelCase, 80 chars width, ...)
- we have a brand new testing framework (still QUnit based)
- kanban view moved to the web addon
- calendar view (formerly web_calender) moved to web as well
- the tree view was removed
- all new code should be documented

We hope that this code is the start of a new era for the Odoo web
client, we want to have a high quality codebase, well documented, well
tested, well designed.

Work done by the framework team: mostly aab, ged, chm, dmo, qsm

Before this commit, if the loadJS method was called two times with the
same url, the associated script was effectively put in the DOM only one
time. However, the second call returned deferred was immediatly
resolved while the script (added by the first call) might not be fully
loaded yet.

Now, calling loadJS for a same url multiple times will always return
the same deferred, resolved when the associated script is fully loaded.

* Remove dead code + optimization
* Use Dialog API from web module
* Reorganize files
* Correct buggy $() function for snippet option class
* Add comments

* Fix the snippet parent navigation :

If a page contained a three level snippet structure (i.e A contains
B contains C), when editing the following bug occured :

If B or C was selected first, parenting buttons were correctly set.
But if selecting A then C, clicking on the parent lead to going back
on A instead of going on B.

* Fix snippet thumbnail layout
* Better isolate ui css from themes
* MediaDialog image list : prevent displaying empty attachments
* ...

Avoid duplicating web addon in enterprise by extracting a common basis.
Enterprise features stay in enterprise, but use that common basis.

Mainly:
 - JS refactoring and linting
 - Conversion of .sass into .less split into multiple files
 - Templates cleaning and DOM simplification
 - Re-generation of web.pot, and update of .po files

e8a00bc50da435d3859118ca127d20a2eb9a0cab moved the get_file function
from web.session to web.ajax. The issue is that get_file uses
session.url() for iOS devices. Also, in order to prevent an infinite
spinner options.complete() is called before actually opening up the new
window. Although this resolves the issue it still requires the user to
configure Safari to allow pop-ups, otherwise they are silently ignored.

opw-672882

In test mode, only one cursor is available, and longpolling will take
it, and not give it back before 60s, causing a phantomjs timeout.  This
commit simply return an error when the server is in test mode.

Sadly, I had to patch the web client to prevent logging the error in
this case, because that's the way phantomjs detect if there is a
problem.

* add CSRF token as core.csrf_token
* add CSRF tokens to client-generated and/or JS-submitted forms
* remove broken "compatibility" mode of web.ajax.post

  /cc @dmo-odoo I've no idea how that was supposed to work, from looking
  things up all modern browsers seem to support FormData, and old IEs
  which don't don't support fallbacks either and would require
  submitting an actual form as fallback so...

Contains a new ajax post function that comes from mdo's
original code and that I was not able to get rid of.