Add doxygen groups "Apparatuses" and "Decoders"
  Make sure every class is in a group
  Make sure most classes have a \brief description
  Improve comments for some classes including THcHallCSpectrometer
     and hodoscope classes
  Change some Doxyfile defaults.  Include sources files.

      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.