FAB-1018 MultiChannel API fabric<-->gossip

This commit changes the API the fabric provides to the gossip layer
to conform to latest discussions.
Previously the JoinChannel message was expected to have all peers in the channel,
 now it can have only the anchor peers.
In addition, each peer needs to know in which organization
a fellow peer is, in order to know whether its safe to pass
a block to it or not via state transfer.

Change-Id: I6af5ce21a14bf6c4eaf1416aefe2877a147f15ec
Signed-off-by: Yacov Manevich <yacovm@il.ibm.com>

gossip/api/channel.go

@@ -25,13 +25,15 @@ import (
 // SecurityAdvisor defines an external auxiliary object
 // that provides security and identity related capabilities
 type SecurityAdvisor interface {
-	// IsInMyOrg returns whether the given peer's certificate represents
-	// a peer in the invoker's organization
-	IsInMyOrg(PeerIdentityType) bool
+	// OrgByPeerIdentity returns the OrgIdentityType
+	// of a given peer identity
+	OrgByPeerIdentity(PeerIdentityType) OrgIdentityType
 
 	// Verify verifies a JoinChannelMessage, returns nil on success,
 	// and an error on failure
 	Verify(JoinChannelMessage) error
+
+
 }
 
 // ChannelNotifier is implemented by the gossip component and is used for the peer
@@ -48,13 +50,16 @@ type JoinChannelMessage interface {
 	// GetTimestamp returns the timestamp of the message's creation
 	GetTimestamp() time.Time
 
-	// Members returns all the peers that are in the channel
-	Members() []ChannelMember
+	// AnchorPeers returns all the anchor peers that are in the channel
+	AnchorPeers() []AnchorPeer
 }
 
-// ChannelMember is a peer's certificate and endpoint (host:port)
-type ChannelMember struct {
-	Cert PeerIdentityType // PeerIdentityType defines the certificate of the remote peer
+// AnchorPeer is an anchor peer's certificate and endpoint (host:port)
+type AnchorPeer struct {
+	Cert PeerIdentityType // Cert defines the certificate of the remote peer
 	Host string           // Host is the hostname/ip address of the remote peer
 	Port int              // Port is the port the remote peer is listening on
 }
+
+// OrgIdentityType defines the identity of an organization
+type OrgIdentityType []byte