-added routines getEdgeVertices and getFaceVertices for returning all
vertices on a face or edge.  Includes some modification to getEdge and
getFace too.
-added ASCII representations of each element type.

INRIA input corrected and enhanced

- removed every "throw;", i.e., every throw that did not throw an actual exception.
  throw wihout args should ONLY be used in a catch{} to re-throw the same exception
  (for it to be handled in another catch clause)

- introduced GmshMessage callback class so that clients can easily implement
  their own message handling (see example in driverOCC.cpp)