Implement the data models for the Mongoid::Storage schema. Probably this will also involve adding some configuration so that developers can specify which database these collections should be stored in.

The data model will consist of Blob, Attachment, and VariantRecord. We should see how feasible it is for VariantRecord to be an embedded child of Blob, but if blobs need to refer to the variant records they belong to, it might be easier to just make them all separate collections.