This is a simple renaming without adaptation.

Browsers' default alignement of <td/> is 'inherit'. Some mail clients do
not set this value properly though and even if it is explicitely set,
they do not compute the final value well.

As a fix, this commit forces the 'inherit' value on <td/> and computes
the real alignment for 'inherit' values when transcoding.

opw-813688

- Not any text by default
- No padding in sent layout (add padding to the editor for readability)
- Apply font size like gmail
- Line spacing should behave like in gmail, so no margin on <p> tags
- Ordered and unordered lists should have proper margin and bullets
  should have black color

Commit https://github.com/odoo/odoo/commit/bee3253b44850c0d563ee8973556ece33376781b
changed the main layout width computation so that it is compatible with
mail clients but broke the preview in the editor.

* 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.

Following bee3253b44850c0d563ee8973556ece33376781b, this commit is made
to increase the mail clients compatibility for the mails that are
created with the odoo mail editor.

Three new problems are handled:

- Font family of titles had to be forced too as outlook was not
  inheriting parent font family on those either.

- Default text font-size had to be forced as was not detected in
  transcoding correctly.

- text-decoration rule was decomposed in text-decoration(-line,
  -style and -color) in transcoding. Outlook is ignoring those
  three rules for some reason. As the decomposition is useless,
  the transcoder now forces the recomposition of these three rules.

Creating a mail template which is complex and compatible with all mail
clients is a very difficult task as each mail client supports a
different subset of basic CSS rules.

This commit fixes 3 problems which were occuring in outlook and/or
thunderbird but not in gmail:

- Main layout horizontal overflow
    -> change 24px horizontal padding of main layout to 3% and set the
       width to 94% (so that the sum is 100%)

- Fixed 600px content was full width instead
    -> Change the .o_mail_wrapper to be a <table> element instead of a
       <div> element. The table is full-width and contains one row of 3
       cells: an empty left one, a fixed 600px-width center one and an
       empty right one. This allows to have the same layout as before but
       without using the unsupported max-width css rule.

- Texts were not using the right color and font-size
    -> <p> elements were not properly inheriting the color and font-size
       properties, so force the style on <p> elements.

opw-743156

* vertical alignment: Keep ‘vertical-align: top’ as default, but
define ‘middle’ exceptions for header and footer snippets.

* ‘comparison_table’: multiline text.
Remove inline style for inner <p/> elements and define default padding
for parent <td/> instead. This will allow to create multiple line of
text keeping a coherent margin between each <td/>.
A css set of rules triggering any kind of elements allow to use
multiline text for any kind of tag (p, h1, etc..)

* Footer snippets padding, minor