Settings: Status Bar transparency and color (2/2)

This introduces status bar transparency and color changes based on an idea
of Roman.

- custom status bar color
- custom status bar transparency
- custom status bar transparency mode (launcher/launcher+keyguard/always)
- reset to default

Patchset 2:
- comment correction

cheers

Change-Id: I414f7553f58fcdc5628a314de19254ac82234cea