The core of this patch is to have the following layout ::

  <nav class="navbar">
    <div class="container">
      <div class="navbar-header">
        [header-logo components]
      </div>
      <div class="collapse navbar-collapse>
        <div class="nav navbar-nav">
          [header-left components]
        </div>
        <div class="nav navbar-nav navbar-right">
          [header-right components]
        </div>
      </div>
    </div>
  </nav>

This prevents the column from collapsing on top of one another if the
screen width is too small. This effectively keeps the 2 column layout at
all screen sizes.

This allows the page content to stretch all the way to left/right window
borders. All width restrictions are lifted.

The X-UA-Compatible directive forces IE9+ to go into IE8 mode, which
never actually behaves like IE8 and actively breaks everything (b0rked
layout, missing text, dysfunctional forms, etc).

Also remove html5.js as it's not shipped anywhere.

This allows writing components using cwtags which monkeypatches
CubicWeb's UStringIO for correct operations.

This fixes a regression introduced by commit 45b3eb604765.

The web browsers are quite tolerant to this but not the (x)html
validators. It is necessary to fix this for e.g. automatic web tests
not to fail.

Fixes a regression introduced by commit 530993d25fe5.

[components] `content_components` (e.g `rqlinput` and `applmessages` components) must be placed before the `div.pageContent` to avoid them vanish after `div.pageContent` reloaded.

closes #3905675

* the contentCol carring layout information (class="col-dm-X")
  is now div#main-center instead of div#pageContent (see cset 1545a8e37c6c)

* HideLeftBar is renamed into HideAsidesBar

Follow up to commit 1c3434c6afd7.

* remove useless classes and id
* add aria-roles

(closes #3553532)

clean the TheMainTemplate