Continue cleanup of C++ code

[jgranick]

Everyone has their own opinion about code style, and what leads to the best workflow, but as a matter of standards, I think it would be best to refactor the C++ project code (over time) to confirm to a single class, with its own header, per file. This additional structure may make it harder to perform sweeping changes within the codebase, but it should make it simpler to maintain, and hopefully lead to less mistakes, and cleaner/clearer pull requests.

[jgranick]

Now that Lime "next" has a new C++ codebase, this shouldn't really be necessary