lnwire: add BOLT#2 channel reestablish message

In this commit the reestablish message have been added, which serves as
channel state synchronization message. Before exchanging the messages
for particular channel peers have to send it to each other as the
first message in order to be sure that non of the updates have been
lost because of the previous disconnect.

lnwire/lnwire_test.go

@@ -563,6 +563,12 @@ func TestLightningWireProtocol(t *testing.T) {
 				return mainScenario(&m)
 			},
 		},
+		{
+			msgType: MsgChannelReestablish,
+			scenario: func(m ChannelReestablish) bool {
+				return mainScenario(&m)
+			},
+		},
 		{
 			msgType: MsgChannelAnnouncement,
 			scenario: func(m ChannelAnnouncement) bool {