Overrides #create_permissions in `Ability` model. This is necessary because included module Hydra::Ability grants create perms to any user on all objects. Yuk.
Moves tests for User permissions on CustomColletions from app/models/ability_spec.rb to app/models/user_spec.rb. I think this is a more logical place for them.
Removes some references to class `Collection`. I think this was a first attempt at ActiveRecord-based collections, but ran into a namespace conflict when trying out Hydra collections maybe, which prompted naming the ActiveRecord-based collection model `CustomCollection`. Need to remove the rest of the old `Collection` stuff.
Removes CustomCollectionController#destroy and tests.