- use surfFaces() to return the templated list of faces.
  This frees up the method 'faces()' to be used as a virtual method,
  which will be needed at a later stage.

Basic featureEdgeMesh functionality.  Dropped intermediate edgeMesh, not serving any purpose, moved io into featureEdgeMesh.  Reads and writes from file.  Can construct self from surfaceFeatures object.  This functionality added to surfaceFeatureExtract, writing to constant/featureEdgeMesh.