BHV-15361: FloatingLayer clips out-of-bounds elements properly

...doesn't directly receive clicks, and fits to the screen size.

New `.enyo-untouchable` class added to simplify disabling pointer events on containers.
A few comparisons converted from strict equality to loose for efficiency's sake.
Misc whitespace cleanup.

Enyo-DCO-1.1-Signed-off-by: Blake Stephens <blake.stephens@lge.com>