Refactored the code.  Described use of code in README.txt add general parameters to settings.py.
Meshes can be saved as ply files.
Add basic GUI functionality to load/save files
Rough.py will write out the internal rough cut and an grown external rough cut
OpenGL allows for different ply files to be displayed using user defined colours as well as being hidden.
Merge branch 'master' of github.com:brachyprint/brachyprint
Reintroducing models.py in src.  This needs merging properly later