Add support for client aggregation of metadata from resolution path

[datadavev]

Different types of information are available at different stages along the resolution path. This can be useful for diagnostic (information about identifier and resolver interpretation) and general (information about the resolved resource) purposes. Currently this information is available from individual services via the ?info or more robustly, /.info/ introspection endpoints where supported, however a client must individually contact each service along the resolution chain.

Task here is to implement a web browser page that uses javascript to fetch the resolution chain by contacting /.info services and present that to the user.

Considerations:

• Use content negotiation to distinguish person (web browser, text/html) from programmatic (application/json).
• Endpoints will need to support CORS for the introspection request
• Needs to be consistency in reported metadata for client side interpretation
• Some clients may not use/allow javascript

Prototype implementation on the info_follow branch.