rely directly on the logging module directly instead of through tldp.utils
add the BaseDoctype to all of the modules (even though not all are
implemented)
the config_fragment function becomes a part of each doctype class, allowing
better encapsulation of most/all document type handling logic
the config_fragment function becomes a staticmethod called argparse
add argparse-style support to each doctype module, for path-configurables
also add the runtime discovery of files needed for document handling (e.g. XSL
and DSSSL files)