Beginning the re-design

The current design is not very good, we're scrapping it and moving the
code to a more sane organization.
Added abstract interfaces

This is the basic pattern everything will follow:

A Translator<> translates OpenXmlElements to LaTeXElements using a
GenericFactory<>, which uses an ElementConverter<> to create the proper
class.
Added some concrete implementations

Created implementations of the GenericFactory and Translator interfaces.
Bulk commit - *Elements, Converter, & unit tests

I got behind on commits; rather than adding these piecemeal (possibly in
an inconsistent order), I'll just lump them all together.

I've constructed LaTeXElement mirrors for each of the OpenXmlElements
and am in the process of writing the converter between the two. There
are
also, of course, the tests.