Commented Unassigned: Enum support in WebApi [1584]

WebApi treats Enum type as String and processes Enum type specially.
Since OData V4 supports Enum type, we want to support Enum type in WebApi after OData migrates to V4.
ODataModelBuilder, ODataConventionModelBuilder, serialization, deserialization and query should be modified to support this feature.
Comments: Checkin: enum support for ODataConventionModelBuilder, serialization and deserialization 5341f1a6c3a7b6573102a558d9cfd187ed186b67