Trigger FileObserver from EDriveApplication instead of FileObserverService

- Remove FileObserverService because useless
- Add "StartRecursiveFileObserver()" and "StopRecursiveFileObserver()" method in EDriveApplication. To allow services to stop/start the FileObserver.
- Replace intent for FileObserverService by call in InitializerService by EDriveApplication.startRecursiveFileObserver()"
- Add a call to EdriveApplication.StopRecursiveFileObserver() method in ResetService
- Remove FileObserverService entry in AndroidManifest.xml
- Add a "watching" boolean field in RecursiveFileObserver and "isWatching()" public method