Maneuver Mode to adjust LAN

Added Heading() and Distance() routines to calculate great-circle routes between two points on a unit circle.
Added DeltaVToShiftLAN() to plan maneuver nodes to either the ascending node, or descending node, whichever is closer.
Merge branch 'feature-LAN' of https://github.com/bk2w/MechJeb2 into bk2w-feature-LAN
Merge branch 'bk2w-feature-LAN' into dev

Conflicts:
	MechJeb2/MechJebModuleManeuverPlanner.cs
	MechJeb2/OrbitalManeuverCalculator.cs
Reformating and fixing previous merge error