12/19/2001: 0.2-1
  new features:
  * provides a som.train function which can perform som training interactively with user inputed code matrix, learning rate, learning radius, training length, etc. 
  * provides a som.update function to update a `som' object from updated training parameters.
  * provides a som.project to project new data onto the map

  Inplementing:
  * changed the underlying c++ matrix classes from lapack++ to tnt.
  * changed .C interface to .Call.

