Commiting so I can switch branches on my computer

- Changed how I store missing data in the periodic table (I let None do
its job)
- Started laying the groundwork for new types of reactants and reactions
- Got rid of some old stuff I don't need anymore
- I'm probably going to want to go and refactor (or at least reread) all
of my old code before I start taking the next big steps
- I'm also going to need to start making a GUI, because a lot of the
real logic is going to go into that.  Going to start with kivy.  I might
give up, though