Dir fix for iframes and widgets

This fix adds a directionality property to the frame objects so directions
can be inherited and manipulated inside the frame <body> tags.
There are also several corrections to flipping positioning of panels
in the GridLayout and of the icons in fieldsets and labeled elements
so they appear properly (right instead of left).

I've added a 've-rtl' / 've-ltr' class to frame content divs to serve as
selectors for rtl fixes and general language fixes. Most CSS corrections
would likely be fixed when CSSJanus works in iframes, but the selectors
would still be useful.

This sets the stage for directionality inheritance inside iframes,
and fixes most of the problem with the Page Settings window in RTL wikis.
It also fixes all the labels with icons across VE interface.

Bug: 49613
Change-Id: I418e669b0999552167683352acb365a4249ab9cc
Merge "Dir fix for iframes and widgets"