Module system

[alfreb]

We need a proper module system. I guess "included" modules could be built into a separate archive, modules.a, to complement os.a. This way we can always link with the modules, but only the ones reference will be linked in.

[alfreb]

I also think 1 module == 1 namespace

[alfreb]

./mod/my_module Contains module sources and includes.
./mod/my_module.hpp contains a common include for everything required to use the module.

There should be a common makefile for all modules, which builds them all into the same archive, modules.a. The service should link against this, but of course not the OS.

[alfreb]

We've started the includer-project, in a separate repo.