Streamline `IMobileObjectMetastate` Implementation

[JasonBock]

Right now, this interface is implemented by the BOs to use JSON. This is pretty heavyweight. The BO knows exactly what non-public state it needs during a serialization roundtrip, so it can literally save that data for most (if not all) of the fields that are "primitive" types, like int, bool, string, etc. So before CSLA 10 is release, my request is to review this implementation and improve the implementation to reduce the size of the metastate that's saved.