Safari will prevent proper input behavior when user-select none
is applied. It prevents such actions as putting in a room lock
password or setting a room lock password. Other browsers allow
selecting on inputs while user-select is none.

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

This reverts commit b309ef25fd.