base.css is unused since rev. 6768bbfcc02e0f498110cda2ba9adbc2fd23d24c

In languages where the thousands separator is a space, numbers could
be wrapped over multiple lines.

This is a rather large change for developers: from this commit on, we
need to use debug=assets instead of just debug to split assets.

The About menu has been slightly improved as well (the link does not
appear when we are already in debug mode), and an option has been added
in the debugging menu to activate the assets debugging mode.

When editing a line, leave the buttons visible.
Also remove the 3px gap between fields so that readonly field texts
does not move when entering the edition mode.

In most backend views using CTRL+P to use browser printing would only
print an header without the content.

stumbled-uppon-when-checking: opw-659430 opw-660763

As .oe_form_sheetbg was not position:relative, tips position was
sometimes wrong as the statusbar is loaded after the tips positions
are computed.

Like view manager containers, client action containers needed the
overflow:auto property to compute their correct height inside their
flex context. This also allows client action as the reconcilation in
accounting to not care about their height.

(backport of enterprise version)

* JS/XML refactoring
* Allow user to override default options for the picker

Elements which are not displayed (display: none) cannot be positionned
correctly by jQueryUI in a listview editable. Therefore, the solution is
to make them visible (but opacity: 0) during the time their position is
being computed.

This was a problem because a listview editable field may become visible
under some conditions AFTER their position was already computed.