re-subscribe logic

1. Re-subscribe logic in registry handler that loops subscription logic for 3 times
2. Addresses gson serialization issue by providing a simple typeadapter for handling fields of type 'class' as seen in 'Modify' -type change notification.
right, so I was handling deduping of the stream in browser client (see eureka-reg-ctrl.js). Tomaz mentioned it would be a problem once we have notification compaction in place. I think I'll implement clear reset notification instead.