Settings: Volume panel background color && transparency [1/2]

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

PS: make "TRDS default" summary value a resource so
        it can be translated.

Change-Id: Ic788b4ccf1826075a600e53bc6a7c3c8bda50685
Merge commit 'refs/changes/03/12903/12' of https://gerrit.slimroms.net/SlimRoms/packages_apps_Settings into kk4.4