Embed "JSON properties" in OData JSON requests and responses

"JSON properties" are represented in metadata as properties of type Edm.Stream , which may be annotated with the existing annotation Core.AcceptableMediaTypes , listing application/json  to specify that the stream property contains JSON. Streams that are annotated as the application/json media type (or one of its subtypes, optionally with format parameters) through @mediaContentType instance annotation are represented as native JSON in JSON requests and responses, they are NOT represented as a base64url-encoded string values. (Note: this is similar to what we  do in the JSON Batch format for JSON request and response bodies.). The odata.mediaContentType control information is only necessary if the embedded JSON happens to be a JSON string, in all other cases it can be heuristically determined that the stream value is JSON. For dynamic JSON properties represented with inline JSON value the odata.mediaContentType control information is always necessary to distinguish them from dynamic Edm.Untyped properties. The term  Core.AutoExpand  is extended to also apply to (stream) properties, enabling "JSON properties" to be implicitly expanded by the service if it is contained in a JSON response. Auto-expanded "JSON properties" MAY be part of the default selection, i.e. represented inline if no $select query option is specified.