Feature queued cross plugin connect

Adds the functionality to create queued cross plugin connections.

implements and closes https://www.graphics.rwth-aachen.de:9000/OpenFlipper-Free/OpenFlipper-Free/issues/109

as Plugins can use crossPluginConnectQueued to connect a signal from their plugin directly with datacontrol plugin, with reduced boilerplate code.

e.g.

ExamplePlugin.hh:

class ExamplePlugin: public QObject, BaseInterface, PluginConnectionInterface, [...] 
{
   Q_OBJECT
   Q_INTERFACES(BaseInterface)
   Q_INTERFACES(PluginConnectionInterface)
   [...]

signals:
   void crossPluginConnectQueued( QString, const char*, QString, const char*);

   /// example signal which can be used to group objects in datacontrol
   void void dataControlGroupObjects(IdList, QString);

   [...]
   void exampleFunction();
}

ExamplePlugin.cc:

[...]
void ExamplePlugin::pluginsInitialized()
{
   [...]
   emit crossPluginConnectQueued("exampleplugin",SIGNAL(dataControlGroupObjects(IdList, QString)),"datacontrol",SLOT(groupObjects(IdList, QString)));
}

void ExamplePlugin::exampleFunction()
{
   //do whatever you want, especially use the signals you want, but don't create loops
   // e.g. emit a bazillion addEmptObject signals
   [...]
   // finally group them with by emitting the connected signal
   emit dataControlGroupObjects(ids, "fancy group name");
}

@lim as soon as this mr is merged, you can update your OpenFlipper submodule and use the above example to group objects.