Elected leader can now skip prepare phase

Added NoMoreAcceptedPast function to replicatedlog
Refactored peer information management into clusterpeers
Added logic to paxos implementation in proposer
Created proposal management package

Other code now uses generic proposal.Id struct
Wrote threadsafe proposal.Manager
Fixed bug updating firstUnchosenIndex

Also wish golang supported negative indices
Added Success RPC

Chosen values will be propagated in case of proposalId change