Output clearer errors to the user if the UAS reports an error when sending missions.
Also these messages are now all translated.
Added a timestamp to when the mission list was last updated.
This code previously existed, but wasn't always triggered. Now it should be.
Set debug messages for rejected waypoint messages to specify which message was rejected.
Moved some more user-facing UI strings into translation calls.
Merge pull request #671 from Susurrus/missions

Minor improvements to UASWaypointManager.cc