Major overhaul of product model nearly complete.  Refs #30.

Everything works, as far as I can tell, except categories.
Made categories work again.  Finished #30.

The hard part is done.  I need to make a release, check it out in
production, update that database, and make one more release for 1.0
with everything out of the way.
Merge branch 'feature/issue-30' into develop