single slicer instance

check for other instances during startup
send message with command line arguments if found and terminate
listen for those messages and load objects from paths in messages from them

src/slic3r/GUI/MainFrame.cpp

@@ -26,6 +26,7 @@
 #include "GUI_ObjectList.hpp"
 #include "Mouse3DController.hpp"
 #include "RemovableDriveManager.hpp"
+#include "InstanceCheck.hpp"
 #include "I18N.hpp"
 
 #include <fstream>
@@ -234,7 +235,8 @@ void MainFrame::shutdown()
 
     // Stop the background thread of the removable drive manager, so that no new updates will be sent to the Plater.
     wxGetApp().removable_drive_manager()->shutdown();
-
+	//stop listening for messages from other instances
+	wxGetApp().other_instance_message_handler()->shutdown();
     // Save the slic3r.ini.Usually the ini file is saved from "on idle" callback,
     // but in rare cases it may not have been called yet.
     wxGetApp().app_config->save();