Introduce PeerInfo and VotingState

Introduce PeerInfo and VotingState

We need to store the voting state for each per so I created a
PeerInfo class to include, id, address and voting state (represented by a
VotingState enum). The RaftActorContext now stores PeerInfo instances
in its peer map and added methods to access PeerInfo. As a consequence,
RaftActorContext#getPeerAddresses was no longer needed and was removed.

AbstractLeader and Candidate were modified to utilize the PeerInfo to
calculate the majority vote/min replication count, ie ignore non-voting peers.

Previously we had added a FollowerState enum and stored it in the
FollowerLogInformation. Since voting state is now stored in the
RaftActorContext peer info, I removed the FollowerState from
FollowerLogInformation to avoid redundancy and having to keep both
up to date.

Change-Id: I1394511a8db7f0b9df3ed7879c77c1f44f3b143d
Signed-off-by: Tom Pantelis <tpanteli@brocade.com>