Adds flip switch for blacklist/whitelist for project

@yunussasmaz @RISCfuture 

I'm not the biggest fan of how this works.  Note that if a user sets switches from a blacklist to a whitelist, all his previous blacklist settings will be _lost_.  

However, on the flipside, if we decide to use a "use_key_exclusion" metadata field, we'll require a migration to ensure that importers are still working correctly.  

On the fence.  If no comments, I may merge it and come back to the issue depending on complaints.