Menu Flight mode filters

Allow the user to control which flight modes are available
on the menu. Helpful for avoiding hitting "Acro" or some
other mode accidentally.

Fix: #697
Merge branch 'settings_modes' of https://github.com/kellyschrock/droidplanner into settings_modes

Conflicts:
	DroidPlanner/src/org/droidplanner/DroidPlannerApp.java