GN: Added variables and procedures for reading hodoscope parameters found in:
xhodo.pos and xhodo.param
THcHodoscope generally holds:
- singular variables (i.e. central path through the spectrometer, min/max limits for the ADCs, TDCs, etc.)
- "padded arrays" (i.e. look at the plane with the most scintillators, allocate and array that has max_no_scint * no_of_planes - these are mostly found in the .param file)
THcScintillatorPlane generally holds:
- simple variables containing plane-specific info (z-position, scintillator size and spacing)
- arrays sized appropirately for the specific plane (i.e. individual x (or y) positions for all scintillators in a plane, signal propagation speed in the paddle, etc.)
Drift chamber code work.  Modeled on podd and h_trans_dc.f

      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.
Merge in Gaby's hodoscope updates.