fix DRONE-15

deactivate Drone with Feature flag
improve Gradle build Feature output
add LegoNXT build flag
fix typos
Merge pull request #989 from Catrobat/DRONE-15_drone_buildflag

DRONE-15 - buildflag
Merge branch 'master' into nfcTesting

Conflicts:
	catroid/res/xml/preferences.xml
	catroid/src/org/catrobat/catroid/stage/StageActivity.java