FB: Volume panel background color && transparency [2/2]

Allow user to specify background color and transparency level
    for volume panel.

PS: color now applies instantaneously after setting the preference.
Change-Id: I23a09d302fe090fe4aed6dd9024c73056d14fba1
Merge commit 'refs/changes/14/12914/7' of https://gerrit.slimroms.net/SlimRoms/frameworks_base into kk4.4