Fix issue #17038762: Add API to add entries to the recents list

New API Added to ActivityManager for adding an entry.  See docs
there.

Repercussions:

- I hit a bug in system UI where if the thumbnail has alpha, it tries
  to modify it, but thumbnails are loading immutable so crashes.  Fixed
  this by loading the bitmaps to be mutable.
- Improved dump output of recents; there was a lot of stuff missing.
  Also split the recents dump output from the rest of the activity
  output, since it can be really large.
- Added tests to the lovely ActivityTest app.

Bonus: new method on AppTask to control the exclude from recents flag.

Change-Id: I01e543db4d15320ee1701e95872fef73c116526c
14 files changed