Remove Google Play Services

As per https://github.com/SecUpwN/Android-IMSI-Catcher-Detector/issues/121 this pull request removes the need for Google Play Services, and instead replaces it with OsmDroid for the map view. The signal strength circles are not implemented yet, and the map type preference is also not yet implemented, but open cell id towers and local tracked towers are displayed with blue and green pins, respectively.