Implement clang-format & clang-tidy

[twostars]

We should have consistently enforced code-styles so we don't have to remind people to keep it consistent manually.

I was looking into clang-format a while back (see the clang-format branch), but skimming over results, I could never produce an output I was happy with.

There's a lot of cases where it was making code considerably more unreadable. I'm not sure if that's just the nature of the beast or if I suck at setting it up, but it really seemed like it wasn't quite flexible enough.

I'm not sure if there's an acceptable level of "awful" for the sake of consistency though.

Also clang-tidy should really be a thing as well for its stricter code validation.