Finish implementing Protractor-style computations.

Also changed computation for bestPossibleSpeedAtImpact to what I *think* is the right equation.
Add an optional "home" crosshair to the steerable camera.
Merge remote-tracking branch 'upstream/master'

Conflicts:
	RasterPropMonitor/Core/PropMonitorComputer.cs
Merge pull request #14 from MOARdV/master

Finish Protractor functionality, plus steerable camera home crosshair