Investigate supporting the :named paramstyle for comdb2.dbapi2

[godlygeek]

Comdb2 now supports this parameter style, and it's easier to use (and doesn't require escaping % characters in the query itself). Investigate whether there's a migration path to recommending this parameter style by default. It would be ideal if we could find a way to support both parameter styles simultaneously and detect which is being used, but failing that we could consider a parameter to connect to control which style is used.