Basic UI to visualise server state

[breezykermo]

datasheet-server should provide a basic interface for a non-technical 'data administrator' to manage updating the server from its sources.

This interface should include:

• An 'update' button (GET request to /api/update)
• A visualisation of current blueprints (available as JSON at /api/blueprints)
• A display of example routes available on the instance (interactive API explorer?)