Merge pull request #50 from MOARdV/master

Add Ascent Guidance enable/disable to MJRPMButton.
Muahaha

Closes #49
That should prevent problems with crew in parts with no IVA.
Redo the guts of the Protractor code to support computations for any type of target (CelestialBody or Vessel).
Update targetClosestApproach computations, and ...

Replace the computations for TARGETCLOSESTAPPROACHTIME and TARGETCLOSESTAPPROACHDISTANCE, since the existing computations are very unstable.