Gentlenav quad

gentlenav multicopter

Branch MatrixPilotMulti supports only UDB4 and AUAV2 at present.

It may eventually support later versions of UDB and AUAV, but likely not UDB3 or AUAV1.

There probably won't be any navigation or RTL support until it's merged with trunk.

https://groups.google.com/forum/#!topic/uavdevboard/MziTW-9SnI8