ESGF node information stored in db instead of requiring registration.xml

[sterlingbaldwin]

RIght now, every time the dashboard loads, it parses the registration.xml for ESGF node information. Instead, that information should be stored in the django database. Additionally, we currently only check the pcmdi9.llnl.gov node for its registration file, instead we should query all visible nodes, and build up the db of node information. This way there wont be as much volatility of node list size, and we will have a list of all nodes that have appeared on the network.

[sterlingbaldwin]

I would also like to refactor the ESGF UI to use a tree instead of the carousel. The only reason I put the carousel in there was because it was in the mock up, not because it actually made sense from a UI perspective.

[sterlingbaldwin]

Im going to hold off on this until the node manager is working.