Modularize

Now that you have made a breaking change (though old code still works, but should be recompiled), what about some changes in this way? Now that you can load packages from different paths, you can modularize the system a little (I always saw `js` as a mirror of `st` for compilation - those other files bugged me).

This is not a pull "request", more an idea to discuss. It can go further (to have IDE(s) in their own folder, for example).