Issue 1711 [Part 1] - When returning an Entity that contains an ETag
annotation, the ETag header should also be set.
https://aspnetwebstack.codeplex.com/workitem/1711

Created an ODataETagMessageHandler to take care of calculating and
adding the ETag Header to the response when it's a successful response
that returns a single resource with an ETag defined and the response
status code is different than NoContent.
Issue 1711 [Part2] - When returning an Entity that contains an ETag
annotation, the ETag header should also be set.
https://aspnetwebstack.codeplex.com/workitem/1711

Created a specific MapODataServiceRoute overload to make registering
per route HttpMessageHandlers in OData routes easier.