Moving InstanceInfo related classes to a new package
Fix integTest shutdown
Refactoring Sourced EurekaRegistry into eureka-core
- Moving Sourced Registry and Preservable Registry to eureka-core
- Using a persistent preservable registry in eureka-client. During interest channel
  failover, the registry content is sent to the eviction queue.
- Fixed a big with the EvictionSubscriber that drops one item when going into self preservation
- Cleaned up close() and shutdown() behaviours for a bunch of classes
- Test updates and fixes