Add digital cam shoot using rc channel
	new file:   conf/modules/digital_cam_shoot_rc.xml
	modified:   sw/airborne/modules/digital_cam/dc.c
	new file:   sw/airborne/modules/digital_cam/dc_shoot_rc.c
	new file:   sw/airborne/modules/digital_cam/dc_shoot_rc.h
	modified:   conf/modules/digital_cam.xml