added vim swap files to gitignore
Writes from MainApp and reads from the UI thread were potentially unsafe for MainActivity::mGpsSats and MainActivity::mGpsFixes

* added an IMainActivity to specify a threadsafe interface against MainActivity.
* modified MainActivity so that updates to mGpsSats and mGpsFixes are thread safe.
wired up the ACTION_NMEA_RECEIVED intent into the Reporter so that we only create StumblerBundle instances if we've got NMEA data within the last minute.
removed this and extra whitespace