mission result topic: Add warnings

msg/mission_result.msg

@@ -2,6 +2,7 @@ uint32 instance_count # Instance count of this mission. Increments monotonically
 uint32 seq_reached		# Sequence of the mission item which has been reached
 uint32 seq_current		# Sequence of the current mission item
 bool valid			# true if mission is valid
+bool warning			# true if mission is valid, but has potentially problematic items leading to safety warnings
 bool reached			# true if mission has been reached
 bool finished			# true if mission has been completed
 bool stay_in_failsafe		# true if the commander should not switch out of the failsafe mode