commander/mavlink: use home attitude, not only yaw

According to the mavlink spec we should be publishing the home attitude
as a quaternion rather than just the yaw/heading.

Additionally, this allows setting the landing roll and pitch angle using
DO_SET_HOME (this yet needs to go into the MAVLink spec though).

This time including the message versioning and translation.

msg/px4_msgs_old/msg/HomePositionV0.msg

@@ -0,0 +1,23 @@
+# GPS home position in WGS84 coordinates.
+
+uint32 MESSAGE_VERSION = 0
+
+uint64 timestamp			# time since system start (microseconds)
+
+float64 lat				# Latitude in degrees
+float64 lon				# Longitude in degrees
+float32 alt				# Altitude in meters (AMSL)
+
+float32 x				# X coordinate in meters
+float32 y				# Y coordinate in meters
+float32 z				# Z coordinate in meters
+
+float32 yaw				# Yaw angle in radians
+
+bool valid_alt		# true when the altitude has been set
+bool valid_hpos		# true when the latitude and longitude have been set
+bool valid_lpos		# true when the local position (xyz) has been set
+
+bool manual_home	# true when home position was set manually
+
+uint32 update_count 	# update counter of the home position