New PR for adding extra channels to Mavlink MANUAL_CONTROL

Proposal to extend the manual_control MAVLink message for extra channels. See Manual Control add 4 more joystick axes (channels 5-8) and RFC 0015 - Mavlink MANUAL_CONTROL message extension PR

This is done for pushing extra channels from QGC. I will update this thread with the QGC PR for calibrating the additional axes and mapping them to the radio control channels.

Thanks @m1kelyons - appreciate this, and you taking the time to post RFC (and PR!). I’ll try get it reviewed in this evening’s MAVLink meeting.