QmlDebugger: Added dialog "Attach to QML Port..."

The dialog is added to Debug->Start Debugging menu option. It specifies the host
and port that the JSDebugClient connects to for listening to debug messages.

Change-Id: I7f828c169ff2338f4780025f72182c5fc8784c4a
Reviewed-on: http://codereview.qt-project.org/4824
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Kai Koehne <kai.koehne@nokia.com>

src/plugins/debugger/debuggerrunner.cpp

@@ -475,6 +475,9 @@ static QList<DebuggerEngineType> enginesForMode(DebuggerStartMode startMode,
         // For now thats the only supported IPC engine.
         result.push_back(LldbEngineType);
         break;
+    case AttachToQmlPort:
+        result.push_back(QmlEngineType); // Only QML can do this
+        break;
     }
     return result;
 }