Clarify that a server MUST respond with content-id annotations and MUST include nested entity IDs

New wording for 11.4.2.2: Clients MAY associate an id with individual nested entities in the request by using the Core.ContentID term defined in [OData-VocCore] . Services that respond with 201 Created SHOULD annotate the entities in the response using the same Core.ContentID value as specified in the request. Services SHOULD advertise support for deep inserts through the Capabilities.DeepInsertSupport term, defined in [OData-VocCap] ; services that advertise support through Capabilities.DeepInsertSupport MUST return the Core.ContentID for the inserted or updated entities.   Clarify that the response must include the entity ID (or all key properties if conventional IDs are used) for all entities returned in the response for a create or update.