Update Conformance section

[csarven]

re #conformance

See for example these sections and subsections (we can revisit the details here):

• https://solidproject.org/TR/notifications-protocol#conformance
• https://solidproject.org/TR/protocol#conformance

This is arguably the most important part of the specification. Make sure to define or refer to classes of products (implementable things by the specification) in Terminology, and then refer to them throughout the Conformance section as to what's expected to conform, what will interop etc.