Remove TAKEOFF from mission item fragment type list if there is more than 1 item in mission list
Allow LAND and RTL mission items to be set only in the end of mission list
Fix TAKEOFF item handling
Stop new mission items addition after RTL or LAND
Moved External libraries to Libraries folder
Merge pull request #959 from alextel69/fix-takeoff-land-sequence

Fix TAKEOFF-LAND (RTL)  sequence

Closes #794
Possible fix to the gradle build
Merge pull request #960 from arthurbenemann/libraries-move

Moved External libraries to Libraries folder