Resolve Recursions with Multiple Exported Objects in C# Generator

At the moment recursive objects are exported as is to a depth. In the C# generator we may be able to resolve recursive object references by generating these objects. This would require a change to the depth solver (and would probably require a C# depth solver and a JSON/XML depth solver).

We likely would not be able to do the same for XML/JSON since we output object values but can't link to another XML or JSON object.

To resolve circular references in JSON I could use the "$id" and "$ref" used by JSON.NET

xml can also use the ref="" attribute