Integrated database

[matthewfl]

Atm, the system currently has leveldb as the backing system for the integrated.

The refactor pull request is changing this to berkeleydb, and I would like to attempt to expose some transactional semantics to the application level.

There is also wiredtiger that looks interesting, as it is written by the same people who originally did berkeleydb. It looks like it has some interesting features such as tranansactions and column and row store modes. Since it can also support indexes, there might also be advantages to using it to manage the data types rather than using protobuf.