SystemUI: allow hiding notification icons
Marquee text RTL improvements

Changed marquee text to scroll according to
the reading direction. Arabic text will
show the right edge and scroll towards
the left edge and vice versa for Latin.

Corrected marquee flicker when scroll animation
finished. The ghost scroll's x position was cast
to int and it made the text flicker when
marquee stops.

Ghost part didn't display for RTL languages.
Added multiplication with
getParagraphDirection to negate the ghost
offset.

Change-Id: I689039118df01a62f73ef0079c857fea1bfcc5a0