Twelfth release candidate for v1.0.0 release

• System does not set a home position any more when already armed and gaining GPS lock
• Missions containing relative altitude waypoints are verboten when no home is set (the system will complain and loiter)
• Fixes for the manual trim capability in manual override mode
• Improvements in the FX79 mixer
• Yaw control retained in high trottle situations for multicopters (@Tumbili)
• HIL usability improvements (Mark Whitehorn)