Transform patterns can be created from multiple base features

The infrastructure/piping seems to have been in place for a long while.
Not tested for all variations of pattern transforms.
The major enabler was removing the `break`.
Some extra piping added to let the code at call-site decide if to select multiple features or not.

src/Mod/PartDesign/Gui/CommandBody.cpp

@@ -286,7 +286,7 @@ void CmdPartDesignBody::activated(int iMsg)
                     Gui::TaskView::TaskDialog *dlg = Gui::Control().activeDialog();
                     if (!dlg) {
                         Gui::Selection().clearSelection();
-                        Gui::Control().showDialog(new PartDesignGui::TaskDlgFeaturePick(planes, status, accepter, worker, quitter));
+                        Gui::Control().showDialog(new PartDesignGui::TaskDlgFeaturePick(planes, status, accepter, worker, true, quitter));
                     }
                 }
             }