add slug to logics

The slug is used as the param portion of a logic-url. It represents a
'cleaner' name where whitespace is replaced with underscores.
Additionally we also replace dots, stars and equality signs with
underscores.
create slugs for existing logics

This migration should contain a safeguard which should ensure that this
never fails (unless there is no logic class i guess...).
use slug to find logics in urls.