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.
Merge pull request #53 from MOARdV/master

Revised Protractor code