Shelled modules.
Ported over old gen-module.bash.

- gen-module.bash is now AGPLv3.
- gen-module.bash now generates AGPLv3 boilerplate.
- All instances where printf expands a variable now use %s.
- Added mk_dir function which is called instead of bare mkdir.
- Added support for generating .mk and .sh files.
- Added a few TODO items.
Ported over paths.source.