Hirshfeld surface fingerprints for new mesh implementation

[peterspackman]

This should be addressed in current versions of the code with the following caveats:

• The new isosurfaces from OCC have far fewer faces for a similar resolution/number of vertices. As such the points sampled for the fingerprint are not just those in the center of each face, but several points per face.
• This should be configurable with a setting or settings, though the defaults should be more than enough for an average user.
• The plot exporting is not where I'd like it to be, but it should be about as good as it used to be.