refactor converters

In preparation for adding new definition and value sources (argparse, python modules, ...) I've refactored the converters.  They're now sorted into to types: to string and from string.  Both types now have dispatch functions that will relieve clients of this module from having to find the appropriate converter manually.
Most likely it's me being dim and still having my vacation hat on but I really don't understand this explanation. It's really cryptic and sadly I can't come up with anything more constructive than to suggest you add some very plain but realistic examples.