Added convenience constructors to Node and Edge that allow specifying a type, name, and content without the user needing to explicitly create an EntityKeys object
Implemented edge counting by type. Other count methods now return long instead of Long
1) EntityKeys no longer support names. With CouchDB, they're redundant (at least with the views we currently have).
2) Also removed most traces of MongoDB. The implementation was falling behind, and it's unlikely we'll need it again anyway.

These updates make views easier to construct and the codebase much easier to maintain.