FAB-1065 Gossip leader election scaffolding

This commit is a scaffolding for a to-be implemented
leader election module that is going to be used for peers
of a same organization to all agree on a single peer
that will connect to the ordering service

https://jira.hyperledger.org/browse/FAB-1065

Change-Id: I1dd04aad05a7cd524c2ef1d6dd55daa537eaa68a
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

gossip/election/election.go

@@ -0,0 +1,45 @@
+/*
+Copyright IBM Corp. 2016 All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+		 http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package election
+
+import (
+	"github.com/hyperledger/fabric/gossip/common"
+	"github.com/hyperledger/fabric/gossip/proto"
+)
+
+// LeaderElectionAdapter is used by the leader election module
+// to send and receive messages, as well as notify a leader change
+type LeaderElectionAdapter interface {
+
+	// Gossip gossips a message to other peers
+	Gossip(msg *proto.GossipMessage)
+
+	// Accept returns a channel that emits messages that fit
+	// the given predicate
+	Accept(common.MessageAcceptor) <-chan *proto.GossipMessage
+}
+
+// LeaderElectionService is the object that runs the leader election algorithm
+type LeaderElectionService interface {
+	// IsLeader returns whether this peer is a leader or not
+	IsLeader() bool
+}
+
+// LeaderElectionService is the implementation of LeaderElectionService
+type leaderElectionServiceImpl struct {
+	adapter LeaderElectionAdapter
+}