- Add a way to generate a FasTCConfig.cmake file so that you can
use cmake without having to install it.
- Add install paths for users that want to install it.
- Hide all public headers in FasTC/ qualified include path, this way we
know what files are public directly from the source. Also, it lets us
define build-tree and install-tree include directories a lot easier.
Start with small tests to make sure that integer sequence encoding is working the way
that it needs to. Ideally there will be many more tests here, but for now we are trying
to get ASTC decompression working and testing is not a priority.