That way, changes can be tracked.
Also, we make it official.
Future checkins will only be made if major changes were done,
similar to how the APIs are handled.
Related to #64
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
