Implement support of cyclical data structures.

Right now if we try to generate field configurations on a cyclical data structure the reflection logic will generate a stack overflow due to recursing too many times.

One way I have been thinking about fixing this is to keep a map of types to field configurations during the generation phase. If we encounter a type a second time we just reuses the memoized field configuration and do not recurse. I hacked this in there and it seemed to work but I probably should do it in a little cleaner way.