It can be selected for each type of program we want to build, and makes
sense for everything that is not a library.
We also tried to unify names and folders a bit more, even though there
certainly is more work to be done to be fully non-redundant.
Fixes#43
This allows us to build efficiently. CLI programs can now have their
own cmn.rs implementation, which we can test standalone with
`cargo test`.
The primary makefile currently just explicitly pulls in the type-*.yaml,
one day we could possibly put it into a loop.
Fixes#11
