"Kind" property should be optional for EntitySets in JSON Service Documents

In JSON, service documents are returned as an array containing objects that represent entitysets and named entities, as shown below. By far the most common of these is "EntitySet", which is consistent with legacy OData services. We should make the "kind" property optional for objects in the service document that represent entity sets.

{
"odata.metadata": "http://host/service/$metadata",
"value": [

,

,

]
}