Some improvements to the manage apps code:

- Battery stats now aggregates bluetooth usage.
- Battery stats now uses new history iterator API.
- Battery stats chart is refectored to have the start of a
  common facility for building tick charts.
- Manage apps will now asynchronously wait for the apps list
  if it is taking >.25ms to build.

Change-Id: I568dd74beedf9a0a5a4c88ab567510cee9af8299