On system update for device owner delete new system apps if required.

On system update, in the device owner case: if the system-apps file is present,
delete non required apps. Otherwise, don't do anything.
Refactored bits and pieces especially the prebootlistener.

BUG:17465315

Change-Id: I1d70d3eccba6ab59deff984a404bb59f617afa63
2 files changed
tree: c42b50107a9280fad9c7f93d7e3a80aa2c145fe8
  1. res/
  2. src/
  3. Android.mk
  4. AndroidManifest.xml