Entries by type

Add the ability for the container to list all entries of a specific type.  This is part of an effort to fix the Ember Inspector's Data tab compatibility with module based resolvers (such as EAK).

99% of the work was done by @yapplabs @lukemelia @stefanpenner @brendanoh over the course of 2 months.

I'm just going to complete the remaining todos and make sure it's ready to be merged and works well with Ember Inspector.  I hope to finish it this weekend.