Add missing parent for messagebox and other popups

Unparented popups can easily get lost in backround, but they still block top level event loop when run with ::exec() thus preventing interactions with main window.  This mainly happens on wayland. Setting the parent ensures they are always kept on top and reasonably positioned.

src/Mod/Points/Gui/Command.cpp

@@ -112,7 +112,7 @@ void CmdPointsImport::activated(int iMsg)
             auto center = bbox.GetCenter();
 
             if (!bbox.IsInBox(Base::Vector3d(0, 0, 0))) {
-                QMessageBox msgBox;
+                QMessageBox msgBox(Gui::getMainWindow());
                 msgBox.setIcon(QMessageBox::Question);
                 msgBox.setWindowTitle(QObject::tr("Points not at Origin"));
                 msgBox.setText(QObject::tr(