This is a HUGE performance increase in development mode. Before this
Active Admin was reloading on every single request to the servers
(assets included). Now we only reload the Active Admin files if
something in the AA load paths has changed.
I18n keys we're being generated using Scope#scope_method which can be
nil sometimes. To fix this, we moved to #scope_method || 'all'.
Instead of this approach we can reliably use #id, which will always
return a sane key.