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/versioned/HomePosition.msg

@@ -1,6 +1,6 @@
 # GPS home position in WGS84 coordinates.
 
-uint32 MESSAGE_VERSION = 0
+uint32 MESSAGE_VERSION = 1
 
 uint64 timestamp			# time since system start (microseconds)
 
@@ -12,6 +12,8 @@ float32 x				# X coordinate in meters
 float32 y				# Y coordinate in meters
 float32 z				# Z coordinate in meters
 
+float32 roll				# Pitch angle in radians
+float32 pitch				# Roll angle in radians
 float32 yaw				# Yaw angle in radians
 
 bool valid_alt		# true when the altitude has been set