Clarify that nested next links can appear on the same page as a delta link

Clarify that each page of results within a response can have either a nextlink or a deltalink but not both. Probably best to avoid the use of the word "page" as it is ambiguous. Maybe something like "The delta payload, and each nested collection within the delta payload, may be paged. The delta link appears on the last page of each collection in place of the nextlink." Also clarify that following nested next links within a delta payload typically doesn't result in a delta at the end-the delta is tracked by the top level response. Clients MAY request the delta link when requesting the nested content and, since it's a preference, the service MAY ignore it. This should be a non-normative clarification.