Merge pull request #2 from BenFrantzDale/DataModel

Added DataModel.py -- a start for a proper data structure for doing the ...
Updated lens_data to work with DataModel.
The data model mostly updates correclty, except the GL view doesn't on initilal file load.
Clean up paraxial ray calculation for clarity WRT ABCD analysis.
Cleaned up paraxial_ray.
Now OpenGL draws on initial load.
Paraxial ray aiming seems to be working.
Ray aiming from infinity, sortof.