Added documentation of each file.

Added documentation of each file.
Re-enabled RAW I/O using AliAltroBuffer and AliAltroRawStream.
Re-implemented AliFMDRawStream for better use with AliAltroRawStream.
Added strip range to calibration parameters.   Perhaps I also need
a calibration that says how many pre-samples the ALTRO makes.  Currrently
with the hardware we have now, it seems that the ALTRO makes 4 pre-samples,
regardless of the oversampling rate.   However, we've only varied the
VA1 shift clock (between 5 and 1.25MHz), relative to 10MHZ for the ALTRO
sample clock.   It may be that the number of pre-samples is a constant time,
which means it depends on the actual sample clock frequency.  If that's the
case, then this parameter should be stored with the sampling rate parameter.
If not, then it should probably be stored independently.

I'm seriously considering making a base class, AliFMDIndex, like

   struct AliFMDIndex {
     UShort_t fDetector;
     Char_t   fRing;
     UShort_t fSector;
     UShort_t fStrip;
   };

and have the `per-strip' classes derive from that, like

  class AliFMDHit : public AliHit, public AliFMDIndex { ... }
  class AliFMDDigit : public TObject, public AliFMDIndex { ... }

What does the experts think about that?