Doxygen documentation support

To run:
Enter Core directory
run 'doxygen' on a terminal
Added DroidPlannerService to take over the role filled by DroidPlannerApp.
Updated the bluetooth device selection interface.
(currently not building).
Version: Releasing version 2.8.1
updating the code to reflect the use of the new api.
(code doesn't build yet)
Android: Fix string on Magnetomer calibration
Merge pull request #1205 from DroidPlanner/issue1201

Android: Fix string on Magnetomer calibration
Android: Removed the help menu
Merge pull request #1207 from DroidPlanner/helpless

Android: Removed the help menu
code update
Core: Add Guided_Velocity control
Merge pull request #1208 from arthurbenemann/doxygen

Doxygen documentation support
Desktop: Catch possible NPE
Core: added structure to hold the footprint locations in the Drone object

Conflicts:
	Core/src/org/droidplanner/core/drone/DroneImpl.java
	Core/src/org/droidplanner/core/drone/DroneInterfaces.java
	Core/src/org/droidplanner/core/model/Drone.java
Desktop: Plot the camera Footprints on the map
Merge pull request #1209 from arthurbenemann/nav_velocity

Guided Nav velocity
Merge pull request #1210 from arthurbenemann/camera_feedback

Camera feedback
Core: add camera trigger functionality
Merge pull request #1211 from arthurbenemann/cameraControl

Core: add camera trigger functionality
fixed location of the side panel drawer image.
Merge branch 'master' of https://github.com/DroidPlanner/droidplanner into ui_cleanup