Clang format

[BearishSun]

Add a clang format file to enforce code style rules.

[jonesmz]

You might consider using a script similar to this: https://github.com/smaeul/uncrustify-auto

That one, uses uncrustify, but it's probably not too hard to convert it to clang format.

[cwfitzgerald]

I have a cmake clang-format script sitting around. It is currently a little crusty (relies on bad cmake style), but if I clean it up I would consider donating it to the cause :)