Clarify Delta responses with Minimal Metadata

Within a delta response, @odata.context is used to convey that a link has been added, or that a link or entity has been deleted, and @odata.id is used to convey id of an added or updated entry.

In minimal metadata, we say that data that can be computed on the client can be omitted. Clearly the context url is still required for added links, deleted links, and deleted entries, as well as added/updated entities from sets other than indicated by the response context url as that cannot be computed from the payload. the id may be computed from the payload only if the payload contains the id fields, and since a service is allowed to return only changed fields then it must also include the id for added/updated entities, even in minimal metadata. same is true for @odata.deltaLink on the last page of the response for retrieving additional changes.