Current user experience:
- User creates a collection (without specifying configset), and makes some schema/config changes.
- He's/She's not happy with how the changes turned out, so he/she deletes and re-creates the collection.
- He/she observes that the previously made settings changes persist. If he/she is only aware of Schema and Config APIs and not explicitly aware of the concept of configsets, this will be un-intuitive for him/her.
DELETE collection should delete the configset if it has the prefix ".AUTOCREATED" and that configset isn't being shared by any other collection.