Wagn.rb

These are all plausible candidates for cards (in Ethan's order of most to least desirable)

• site name
• invitation request email
• error emails: recipients, sender, subject prefix,
• max render time
• max renders

These can be overwritten by cards already.   I kind of think we should deprecate them in wagn.rb:

• invitation email subject / body

These I suspect make sense to leave to system administrators, at least for now:

• base url
• enable postgres full text
• postgrest search dir
• type of cache store

Other configurables

One of the hardest things to update now (and most often requested) is local.css

database.yml configs probably still belong in administrator's hands.