PhoneWindowManager: cleanup and improve content observer handling

this settings observer is massive.  probably a good idea to provide
a check and nullify in case there's a crash and it's going to get registered
again.  Also, do the same with the broadcast receiver for screenshot/power menu.
more to come.

Change-Id: I90b301c3d45aca7b26ba5dbb3fa1b32be2ec957f
potential GraphRunner leak in camera effects

if the camera FCs while recording effects.. *poof* a tiny leak is born.
so.. we close mRunner onDestroy.

Change-Id: I6a7983f120a03137f545a3cd9bb07ff51a9cd2d7
Merge changes I6a7983f1,I90b301c3 into jb43

* changes:
  potential GraphRunner leak in camera effects
  PhoneWindowManager: cleanup and improve content observer handling