removed unused imports to clean up some warnings
minor cleanup in LocationUpdate getPosition()
added EventType enumerated type to wrap up data about event types (DB value, display value, and drawable ID so far)
added support to LocationUpdate model for getting and setting the EventType object for an instance
added support to Event model for getting and setting the EventType object for an instance
CreateEventActivity: switched over to use new EventType class
FilterActivity: switched over to use new EventType class
MapDemoActivity: refactored to use new EventType class
GPSTracking: null check the gpsListener in onLocationChanged() for now to avoid a crash