Determine readout side in THcDriftChamberPlane at initialization time.

1) THcDCWire.h
  a) added sigma to THcDCWire constructor which fills fSigmaWire
  b) added GetSimga method
  c) added SetSigma method

2) THcDCHit.h
 a) Added GetWireSigma method

3) THcDriftChamberPlane.h
 a) Added flag fUsingSigmaPerWire
 b) Added array fSigmaWire

4) THcDriftChamberPlane.cxx
 a) In ReadDatabase, set fUsingSigmaPerWire=0 by default
    with reading of parameter h_using_sigma_per_wire optional
    for setting fUsingSigmaPerWire.
 b) If fUsingSigmaPerWire=0 then sets all wires in array fSigmaWire to
   fSigma ( which is the simga per plane).
 c) If fUsingSigmaPerWire=1 then reads in the sigma per wire from
   a parameter file.
 d) Used new THcDCWire constructor to set the sigma for wire to fSigmaWire[nwire]
 e) Also change code so that the tzero offset is set in the  THcDCWire constructor
 f) In ProcessHits , use wire->GetTOffSet instead of the fTzeroWire array when setting
    the time.

5) THcDC.cxx
 a) In TrackFit, replace fSigma with hit->GetWireSigma()

THcSpacePoint
  1) added fSetStubFlag which is intialized
     to kFALSE in constructor and set to kTRUE
     when SetStub is called.
   2) added method GetSetStubFlag which
      returns fSetStubFlag.

THcDriftchamber
   1) In ProcessHits increased fHits reserve to 40
   2) In FindSpacePoints use fSpacePoints->Delete();
   3) In LeftRight ,only SetStub if the Stub is fit.

THcDC
   1) In LinkStubs
      a) only link stubs if number of total spacepoints <10
      b) only link stubs if both spacepoints have SetStubFlag true

THcDCHit.h
   1) In constructor initalize fLR to 0

THcDCTrack.cxx
   1) AddSpacePoint check if fnSP < 10

Add rawnorefcorrtime to THcDCHit which is the TDC raw without
the reference time subtraction.

Add variable rawnorefcorrtdc in THcDriftChamberPlane::DefineVariables

Modify THcDriftChamberPlane::ProcessHits to call GetRawTdcHit().GetTimeRaw
  and call THcDCHit with new extra argument for raw time without reference time
  subtraction.

1) Add X,Y offsets parameter for each plane, instead of X,Y offset per chamber
2) ModifyTHcDriftChamber::CorrectHitTimes to work with SHMS chambers
3) Add GetReadoutSide method to THcDCHit class.

This error is triggered when there is no wire defined for hit, or
when the wire has no `GetTDDConv()` method. The ROOT dictionary
calls default constructor that doesn't set the wire and calls
`ConvertTimeToDist()` regardless.

I changed the default constructor to not call the `ConvertTimeToDist()`
if the wire is not set. I also added the call to this function
in the `SetWire()` method.

   {prefix}dc_fix_lr
        Historically, in the ENGINE, if a hit is used in multiple
        space points/stubs, the left/right assignment for that hit, which
        is later used in track fitting, is that assigned for the last stub
        encountered with that hit.  Properly, the left right assignment
        should be allowed to be different in different space points.  If
        this parameter is set to zero (e.g. in hcana.param), then the
        ENGINE behavior is used.  For new analyses, it should be set to one.
        (Which is the default)
   {prefix}dc_fix_propcorr
        When a hit gets put into a stub, the distance of the hit from the
        discriminator can then be estimated.  In the engine, a correction to
        the drift time (and thus drift distance) is applied.  However, if
        that hit ends up in another stub, the correction will get applied again,
        resulting in a over correction.  Setting this flag to 1 will give that
        hit a different corection for each stub that it is in.

These flags will default to the new "correct" way of handling hits if
the above parameters are not set in a parameter file.  Currently, both
flags are set to zero in hcana.param to replicate the ENGINE behavior.

To implement these changes, the propagation correction and L/R information
for each hit is saved in space point and track classes.  This information
is still saved in the hit class, but only used if in ENGINE compatibility
mode.

The THcDCTrack class now saves a list of space point pointers instead
of space point indices.

The AddSpacePoint method now also copies all the hit information into
the track object so that THcDC doesn't need to explicitely copy all
the hits.

The FindStub method, which fits a stub track to a space point is passed
the space point rather than a list of hits

In the ENGINE, this can happen if a hit belongs to more than one space point.

  New class THcDC is whole set of wire chambers.
  THcDriftChamber is one chamber (6 planes)
  Implement space point finding from h_pattern_recognition up to point
     before where space point lists from the two chambers are combined.
  Includes
      FindEasySpacePoint   (h_find_easy_space_point)
      FindHardSpacePoints  (find_space_points)
      DestroyPoorSpacePoints (h_sp_destroy)
      SpacePointMultiwire  (h_sp_multiwire)
      ChooseSingleHit 	   (h_choose_single_hit)
      SelectSpacePoint	   (select_space_points)

Space points are arrays of structures in the THcDriftChamber class.  Will
probably need to take space points out class so that they can be looked at
at the THcDC level.

New code is only tested to see that it compiles and that space points
are sometimes found.

  It has not been check that we are getting a good start time yet.
  Drift time and distance added to tree
  Change DC plane names from 1, 2, 3, ... to 1x1, 1y1, ...
    This is so that the parameters holding the time to distance maps
       can be found.  (The parameters are e.g. hwc1x1fract)
    Need to find a way not to have to hard code these plane names.
       Either use wire angles (alpha) or some kind of parameter name mapping
  Changed output.def to match new plane names

      Start adding to the drift chamber code.   Setup a class structure
      similar to what podd uses for the VDCs.  Raw hit class renamed
      to THcRawDCHit.  Signal hits are how THcDCHit, modeled after
      podd hits.  Add THcDCWire, and classes for time to distance conversion.
      Time to distnace conversion doesn't do anything yet.

      Find some improved DC parameter files so that min and max TDC limits
      are good for the run we are using.

      THcDriftChamberPlane asks ThcDriftChamber for many parameters.

TClonesArray ConstructedAt method.

Raw hit class for drift chambers and skeleton drift chamber that prints
out drift chamber package hits.

Move Compare method from THcHodoscopeHit to ThcRawHit since it should
work for any derived class.

Get detector name -> ID mapping from the map file comments