The coding style is similar to the one of sorcery. Just play along with the
rest of the code.

Adding download modules
* the name of $MODULE should be unique
* write the download code
* provide a quill_${MODULE}_core function as the entry point for quill
* add unique commandline switches to the argument parser
* add the commandline switches to help
* the module should fall back to the provided spell name if it couldn't
  retrieve one itself
* don't exit on error but return
