improve comments for attitude message

fixes #1828

msg/vehicle_attitude.msg

@@ -4,15 +4,15 @@ uint64 timestamp	# in microseconds since system start
 float32 roll		# Roll angle (rad, Tait-Bryan, NED)
 float32 pitch		# Pitch angle (rad, Tait-Bryan, NED)
 float32 yaw		# Yaw angle (rad, Tait-Bryan, NED)
-float32 rollspeed	# Roll angular speed (rad/s, Tait-Bryan, NED)
-float32 pitchspeed	# Pitch angular speed (rad/s, Tait-Bryan, NED)
-float32 yawspeed	# Yaw angular speed (rad/s, Tait-Bryan, NED)
-float32 rollacc		# Roll angular accelration (rad/s, Tait-Bryan, NED)
-float32 pitchacc	# Pitch angular acceleration (rad/s, Tait-Bryan, NED)
-float32 yawacc		# Yaw angular acceleration (rad/s, Tait-Bryan, NED)
+float32 rollspeed	# Roll body angular rate (rad/s, x forward/y right/z down)
+float32 pitchspeed	# Pitch body angular rate (rad/s, x forward/y right/z down)
+float32 yawspeed	# Yaw body angular rate (rad/s, x forward/y right/z down)
+float32 rollacc		# Roll angular accelration (rad/s^2, x forward/y right/z down)
+float32 pitchacc	# Pitch angular acceleration (rad/s^2, x forward/y right/z down)
+float32 yawacc		# Yaw angular acceleration (rad/s^2, x forward/y right/z down)
 float32[3] rate_offsets	# Offsets of the body angular rates from zero
 float32[9] R		# Rotation matrix, body to world, (Tait-Bryan, NED)
 float32[4] q		# Quaternion (NED)
-float32[3] g_comp		# Compensated gravity vector
+float32[3] g_comp	# Compensated gravity vector
 bool R_valid		# Rotation matrix valid
 bool q_valid		# Quaternion valid