droid: remove the stateful life-cycle manager

Simply properly react to messages instead. This ends up being much cleaner and
more straightforward.

There were many problems with the old life-cycle code:
- It based all decisions on gain/loss of focus, which is incorrect, as that
  pertains to input rather than windowing.
- Due to the above, there were many race conditions.
- The startup/teardown were convoluted
- It was a mix of examples, a stateful one where the app keeps track of status,
  and a stateless one mainly handle by appglue. Since we really only care about
  a handful of events (startup/exit/newwindow/destroywindow mainly), stateless
  is the way to go for us.

This fixes random black-screens, fixes, and crashes when starting XBMC as a
launcher.
droid: fixup thread detach
Merge pull request #2278 from theuni/android-clean-lifecycle

droid: remove the stateful life-cycle manager