Implement Dynamic System Bars [2/2]

This commit implements DSB. Simple as that.
All the changes:
- frameworks/base (I3bc7102b2139fd1fa3de22aac096bd2a75bde878)
- packages/apps/Settings (Id2b105dfb3faf3cad74d0fa0dc33d01f6b71a853)
Change-Id: Id2b105dfb3faf3cad74d0fa0dc33d01f6b71a853