Allow to drag more then one FBNetworkelement accross editor bounds

With this fix also several selected FBNetworkElements can be dragged
across editor boundaries using the alt key and drag&drop.

plugins/org.eclipse.fordiac.ide.application/src/org/eclipse/fordiac/ide/application/dnd/CustomDragSourceListener.java

@@ -82,7 +82,7 @@ private Request createRequest(final Point point) {
 		if (selectedEditParts.size() == 1 && selectedEditParts.get(0) instanceof final InterfaceEditPart iep) {
 			return createConnectionCreationRequest(iep);
 		}
-		if (selectedEditParts.size() == 1 && selectedEditParts.get(0).getModel() instanceof FBNetworkElement) {
+		if (atLeastOneFBSelected(selectedEditParts)) {
 			return createChangeBoundsRequest(selectedEditParts);
 		}
 		final List<ConnectionEditPart> connections = selectedEditParts.stream()
@@ -102,6 +102,10 @@ private static Request createConnectionCreationRequest(final InterfaceEditPart i
 		return req;
 	}
 
+	protected static boolean atLeastOneFBSelected(final List<? extends EditPart> selectedEditParts) {
+		return selectedEditParts.stream().anyMatch(ep -> ep.getModel() instanceof FBNetworkElement);
+	}
+
 	private static Request createReconnectRequest(final List<ConnectionEditPart> connections, final Point point) {
 		final ConnectionEditPart first = connections.get(0);
 		final String reconnectType = getReconnectType(first, point);