Update the color of the expandable volume panel icon

This still retains the old settings icon since it
happens to fit perfectly. Pressing it does indeed
show you a bunch of sliders like the icon indicates.

Also add xhdpi and xxhdpi versions.

Change-Id: I944a325c8871e1afc9d7163b0f23f7f9d8ae070a
Merge branch 'cm-11.0' into cm-11.0-sgt7