mavlink: add onboard function for camera capture commands
mavlink: camera mode with rate multiplier
mavlink: correct verbose info, bytes not bits
mavlink: camera mode rate is now correct
Merge remote-tracking branch 'px4/beta_mavlink2' into beta_mavlink2_camera

Conflicts:
	src/modules/mavlink/mavlink_messages.cpp
Merge pull request #754 from julianoes/beta_mavlink2_camera

Beta mavlink2: onboard camera capture