Handle finished signal for the ReadMeshJob started from command line args

This puts the actual mesh into the scene rather than just loading it and
discarding it afterwards. Now file arguments supplied to the application
actually work.

Fixes "Open With" on Windows and the related Asana issue.

cura/CuraApplication.py

@@ -162,6 +162,7 @@ class CuraApplication(QtApplication):
 
             for file in self.getCommandLineOption("file", []):
                 job = ReadMeshJob(os.path.abspath(file))
+                job.finished.connect(self._onFileLoaded)
                 job.start()
 
             self.exec_()
@@ -447,3 +448,15 @@ class CuraApplication(QtApplication):
     def _onMessageActionTriggered(self, message, action):
         if action == "eject":
             self.getStorageDevice("LocalFileStorage").ejectRemovableDrive(message._sdcard)
+
+    def _onFileLoaded(self, job):
+        mesh = job.getResult()
+        if mesh != None:
+            node = SceneNode()
+
+            node.setSelectable(True)
+            node.setMeshData(mesh)
+            node.setName(os.path.basename(job.getFileName()))
+
+            op = AddSceneNodeOperation(node, self.getController().getScene().getRoot())
+            op.push()