Do partition tolerance of replicas across buddy pools by round robin selection

[simmhan]

Ensure that different replicas are placed on different buddy's or their neighbors. [This Allows the block to survive loss of a single buddy (permanent) and its neighbors (transient).]

Related to loss and recovery of buddy, #22

[skmonga]

During replica identification phase, make sure that the replicas are chosen in such a way that after choosing a replica, we properly maintain a lookup table so that next and subsequent replicas belong to different buddies of the contacted node (buddy itself or one of its neighbors) so that failure of a buddy (permanent) doesn't lead to the data being unavailable and can be corrected using other members of the buddy pool. This concept is similar to the failure-groups concept in FogStore where the fog devices in a single failure-group fail together.