Adding datasets programatically

Added interface to add opendap endpoints to sciWMS programmatically. For example, I wrote a script to automatically parse the NGDC testbed catalogue and used this function to insert the endpoints in the database and populate the cached topology.
Instead of this technique, use `.filter(blabla).count()`, it's more efficient, no objects get returned.  Probably not a big deal given how little datasets are typically in a sci-wms installation but it's best practice.