Add an example of a Client/Server scenario demonstrating profile inheritence

[nicholascar]

From ShEx IG:

We were unsure what to make of "inheritance", as we are not aware of any generalized notion of inheritance that would make sense across implementation technologies. It would be helpful to motivate this with a testable use case, e.g., a server implementation which responds to Accept-Profile by calculating the "best" response for processing a Profile Ontology description. A test of inheritance would include the notion that inheriting imposes further constraints, and that the entity being inherited from may in turn inherit from something else. ShEx shape inheritance has this behavior.

[nicholascar]

The server should attempt to reply with a profile that best matches the client request. The order of preference is an exact match, followed by a profile (perhaps transitively) of the requested profile.

(+EXAMPLE)

[nicholascar]

If a client requests a profile but gets a narrower profile, the Server should set its responses Content-Profile header to the profile identifier that the Client requested, not the identifier of the narrower profile as the client might not understand the narrower profile identifier.

[nicholascar]

This Issue is now addressed by Section 6.2.2 in the document