Set 2d histogram limits on tracking results.

   Add track coordinates to track structure.
   Add code for single stubs
   Try to deal with plane number/index confusion

Updated THcDriftChamber::SpacePointMultiWire
Added debug flag
Updated THcDriftChamber::ChooseSingleHit
Updated THcDriftChamber::SelectSpacePoints

Since we have not yet overwritten the = operator for space points
had to add code to do this.

  Uses ROOT matrix math instead of solve_four_by_four
  Nothing is done with found tracks yet.  Will need to stuff these into
     podd style tracks.  (Or a class inherited from podd style tracks.)
  Residuals not saved anywhere
  Single stub mode not yet implemented
  No printing out of trackfit results (hdebugtrackprint)

Set fDebugDriftCh in DefineVariables
Put if fDebugDriftCh in front of all cout statements
In THcDriftChamber::DestroyPoorSpacePoints replace line (*fSpacePoints)[isp] = (*fSpacePoints)[osp];
In THcDriftChamber::SelectSpacePoints() replace line (*fSpacePoints)[sp_count] = (*fSpacePoints)[isp];

Set fDebugDC in THcDC::ReadDatabase

   for first hit. Added an else branch to increase finalnum
2)  In THcDriftChamber::LeftRight() when using the small angle
    approximation then assignment of sign to the y planes was reversed.

  Compiles and doesn't crash.

  THcDriftChamber::SpacePoint -> THcSpacePoint
  That way space points can be put in a TClonesArray and be made known
  to THcDC when stub information is added.

  1)   Moved hardcoding of Yplane plane number to Addplane since it is called
     before ReadDatabase
  2) In FindEasySpacePoint add variable max_dist to match the code in
     h_find_easy_space_point.f more and fix problem
  3) As in h_find_easy_space_point  use max_dist instead
     of FSpacePointCriterion in IF statement to pick matching "x" hits.
In THCDC.h
  1) Set GetPicth and GetCentralWire as Double_t
  2) Set  GetSpacePointCriterion to return fSpace_Point_Criterion2[chamber-1]
     instead of sqrt