Pull a lot of cruft out of localconfig, it's more code than config
Dynamically build the list of Distiller classes

This saves on repetition, which would be prone to error. We already
explicitly import each Distiller in distil/__init__.py, so we have some
control over what appears in scope.

This method is probably technically undefined, but appears to leave the
`distillers` list in alphabetic order. This should not, but cannot be
guaranteed not to cause problems when we try to find a distiller for a
given URL. We don't expect any problems though, as we probably shouldn't
have more than one distiller that can handle a particular URL.