Revise WatchFace sample's AnalogWatchFaceService.java and

SweepWatchFaceService.java to include an actual picture
background (vs. simple image of w/ fade). Also,
refactored w/ better optimizations and to closer match
the WatchFace codelab (PeekCard support, Palette Color use,
etc.).

Bug: 21732041
Change-Id: I56ec2cf7c8c5e8e90c16fe38f8357694beacdcda