Fixes to connecting to remote databases

This is a few changes.  The commits tell the details, but here is the run down:

* the `url` config had no effect on connecting to databases, moving to `host` and `port` to match up with AR
* extracting a string-keyed hash of the non-nil configs and using that to configure AR
* have the `connect` cmd actually get a connection from the AR connection pool

All this is in response to woes in connecting to remote databases.  The need for most of this was hidden by the fact that I had only been connecting to local databases.

@jcredding ready for review.