MongoDB (DO NOT MERGE)

[pennyfx]

There's a few things on this branch.

1. Works with MongoDB
2. Added model_id to all queries so that things are properly scoped, which surfaced various errors in our tests as well.
3. Removed (home) from all controllers/commands and instead use Config().set_home() function, so that home dir is not passed everywhere.
4. Various refactoring

For mongodb to work properly, there needs to be a way for the user to configure the credentials. Right now it's hard coded here

perhaps something like datmo config --db="mongodb://user:pwd@host:port/db"