The 1:1 call UI and vertical filmstrip act on remote videos
while leaving local video alone. To facilitate acting only on
remote videos, place remote videos into their own container element.
All z-indexes found in css files have been moved into css
variables. If the z-index is used only once, the variable
name will be the same as the selector it is used in. If
the z-index is used multiple times, then the plain name
of $zindex# was used. This allowed a more confident
moving down of the toolbar so that the new modal dialog,
with z-index 500, could display on top of it.
#1436