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.
You could probably use django's [slugify](https://docs.djangoproject.com/en/dev/ref/utils/#django.utils.text.slugify) to create the id from the title, if the user doesn't pass one in.