Vehicle command: Add mission item to gate mission execution on line orthogonal to current trajectory

msg/vehicle_command.msg

@@ -26,6 +26,7 @@ uint16 VEHICLE_CMD_CONDITION_CHANGE_ALT = 113		# Ascend/descend at rate.  Delay
 uint16 VEHICLE_CMD_CONDITION_DISTANCE = 114		# Delay mission state machine until within desired distance of next NAV point. |Distance (meters)| Empty| Empty| Empty| Empty| Empty| Empty|
 uint16 VEHICLE_CMD_CONDITION_YAW = 115			# Reach a certain target angle. |target angle: [0-360], 0 is north| speed during yaw change:[deg per second]| direction: negative: counter clockwise, positive: clockwise [-1,1]| relative offset or absolute angle: [ 1,0]| Empty| Empty| Empty|
 uint16 VEHICLE_CMD_CONDITION_LAST = 159		# NOP - This command is only used to mark the upper limit of the CONDITION commands in the enumeration |Empty| Empty| Empty| Empty| Empty| Empty| Empty|
+uint16 VEHICLE_CMD_CONDITION_GATE = 4501		# Wait until passing a threshold |2D coord mode: 0: Orthogonal to planned route | Altitude mode: 0: Ignore altitude| Empty| Empty| Lat| Lon| Alt|
 uint16 VEHICLE_CMD_DO_SET_MODE = 176			# Set system mode. |Mode, as defined by ENUM MAV_MODE| Empty| Empty| Empty| Empty| Empty| Empty|
 uint16 VEHICLE_CMD_DO_JUMP = 177			# Jump to the desired command in the mission list.  Repeat this action only the specified number of times |Sequence number| Repeat count| Empty| Empty| Empty| Empty| Empty|
 uint16 VEHICLE_CMD_DO_CHANGE_SPEED = 178		# Change speed and/or throttle set points. |Speed type (0=Airspeed, 1=Ground Speed)| Speed  (m/s, -1 indicates no change)| Throttle  ( Percent, -1 indicates no change)| Empty| Empty| Empty| Empty|