Removing methods already existent on SuperActivity.
Removes the MavLink Object in the DroidPlannerApp class.

Use the drone class when sending a message, from there you can access the MavLink object.
Remove duplication by using already written methods.
Refactoring: Extracting another Mavlink message
Merge pull request #180 from arthurbenemann/Refactoring

Refactoring, mostly removing duplication and extracting methods.