Add fDebugDriftCh to THcDriftChamber.h to flag when to write out debug statements

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];