Fixing table name bug - database name in table name should change when c...

...onnection parameters are passed in.

Re: https://github.com/weecology/retriever/issues/127

Ethan, could you check this on MySQL/Postgres before merging?

Also, as a side effect, the database name can no longer contain the table name (otherwise they'd have a circular dependency, and could cause things to hang.) This required changing two of the unit tests.