initial version of msg to uorb script

Standard and embedded types work, may need small refinements for some
types

msg/px4_msgs/actuator_armed.msg

@@ -0,0 +1,6 @@
+
+uint64 timestamp	# Microseconds since system boot
+bool armed          # Set to true if system is armed
+bool ready_to_arm	# Set to true if system is ready to be armed
+bool lockdown	    # Set to true if actuators are forced to being disabled (due to emergency or HIL)
+bool force_failsafe # Set to true if the actuators are forced to the failsafe position

msg/px4_msgs/rc_channels.msg

@@ -0,0 +1,24 @@
+int32 RC_CHANNELS_FUNCTION_MAX=18
+uint8 RC_CHANNELS_FUNCTION_THROTTLE=0
+uint8 RC_CHANNELS_FUNCTION_ROLL=1
+uint8 RC_CHANNELS_FUNCTION_PITCH=2
+uint8 RC_CHANNELS_FUNCTION_YAW=3
+uint8 RC_CHANNELS_FUNCTION_MODE=4
+uint8 RC_CHANNELS_FUNCTION_RETURN=5
+uint8 RC_CHANNELS_FUNCTION_POSCTL=6
+uint8 RC_CHANNELS_FUNCTION_LOITER=7
+uint8 RC_CHANNELS_FUNCTION_OFFBOARD=8
+uint8 RC_CHANNELS_FUNCTION_ACRO=9
+uint8 RC_CHANNELS_FUNCTION_FLAPS=10
+uint8 RC_CHANNELS_FUNCTION_AUX_1=11
+uint8 RC_CHANNELS_FUNCTION_AUX_2=12
+uint8 RC_CHANNELS_FUNCTION_AUX_3=13
+uint8 RC_CHANNELS_FUNCTION_AUX_4=14
+uint8 RC_CHANNELS_FUNCTION_AUX_5=15
+uint64 timestamp_last_valid					# Timestamp of last valid RC signal
+float32[18] channels						# Scaled to -1..1 (throttle: 0..1)
+uint8 channel_count						# Number of valid channels
+int8[18] function						# Functions mapping
+uint8 rssi							# Receive signal strength index
+bool signal_lost						# Control signal lost, should be checked together with topic timeout
+actuator_armed actuator