Create actor lazily and reuse already created/connected actors. Also fix webconsole actor when reusing it more than once.
Bug 887809 - webconsole actor doesn't unregister correctly consoleProgressListener on stopListeners
Bug 887781 - Send message-manager-disconnect notification event when any message manager get disconnected.
Listen for message-manager-disconnect to unregister the message manager in DebuggerClientTransport and stop the prefix forwarding the DebuggerConnection.