(PUP-405) Remove active record stored configs

This removes active record based store configs, and all things rails related from the puppet code base.
@joshcooper are you saying that `clean_storeconfigs` shouldn't be removed but made to work with puppetdb? 

I'm of two minds (and I don't know the historic use cases for `puppet node clean`):
* on the one hand, there's the assumption clean should mean clean everywhere
* otoh I have some concern that it shouldn't be used as a tool for managing puppetdb, especially as we get into richer Node Lifecycle Management scenarios