Remove unused imports
Issue #319 - Remove location update callbacks when the Activity is paused.

* To avoid memory leaks and battery draining, the location updates are
not required when the Activity is inactive. Since the activity has no
direct access to the GeoQuestionView objects and the onPause() callback
has to be propagated, a new interface for QuestionViews is provided, to
allow any subclass to perform system resource cleanup when no longer needed.
Issue #319 - Update UI after releasing the LocationManager updates

* In case we go back to the same instance of the GeoQuestionView
(i.e. navigating within the same Activity), we have to update the
message shown to the user regarding the GPS status.