Issue 1749 - OData V4 service do not properly handle invalid
OData-Version header values (V4 version)
https://aspnetwebstack.codeplex.com/workitem/1749

This fix adds a version constraint to the ODataRoute that will prevent
it from matching any request with a v3 version header or a request
with a v4 version header whose value is different than 4.0.
This constraint will still match any request without version headers.

Conflicts:
	test/System.Web.OData.Test/HttpRouteCollectionExtensionsTest.cs