Additional endpoints for graph subsystems

[vsoch]

We should be able to:

• As the graph to show the structure for nodes (resources) we have access to
• Ask the graph to list subsystems available
• Ask the graph to show metadata per subsystem

And likely formats that feed into visualizations.

[vsoch]

Note that this is somewhat solved by using different graph backends that come with web interfaces out of the box. Transparency of fluxion is another issue.