Adding new data type for Eureka registry that stores multiple copies
of instanceInfo data w.r.t. to different input sources
MultiSourcedDataHolder interface update
Merge pull request #245 from qiangdavidliu/2.x

New data type for Eureka registry
Merge remote-tracking branch 'remotes/netflix/2.x' into 2.x

Conflicts:
	rx-eureka-client/src/main/java/com/netflix/rx/eureka/client/service/InterestChannelImpl.java
	rx-eureka-server/src/main/java/com/netflix/rx/eureka/server/service/ReplicationChannelImpl.java
	rx-eureka-write-server/src/main/java/com/netflix/rx/eureka/server/replication/ClientReplicationChannel.java