added copyright headders to channels

channels/adminListener.go

channels/adminListener_test.go

channels/channelMessages.pb.go

channels/channelMessages.proto

channels/emoji.go

channels/emoji_test.go

channels/errors.go

channels/eventModel.go

channels/eventModel_test.go

channels/generateProto.sh

channels/interface.go

channels/joinedChannel.go

channels/manager.go

channels/manager_test.go

channels/messageTypes.go

channels/messageTypes_test.go

channels/messages.go

channels/messages_test.go

channels/mutateTimestamp.go

channels/mutateTimestamp_test.go