* Fixes some toolbox/toolbar styles and variables

* [squash] Fixes variable name to fit better its purpose

* [squash] Fixes secondary toolbar variable name

Cleanup existing logic for displaying and updating device
selection settings in the settings menu. In its place
is a button to open the device selection modal.

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