Fix NPE from getActivity() call

Use onAttach and onDetach to execute mTask, to be sure that the activity
was created

Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Fix random disposition bug

The mRecreateWorld never set to false, causing the world to be recreated
every time the device resume

Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Reduce synchronized lines

Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Handle back button on ChoosePictureFragment

Signed-off-by: Jorge Ruesga <jorge@ruesga.com>