Inserts a row or column at the specified position.
The new row or column is placed next to sibling, on the side determined by side. If side is
clutter_grid_position_left or clutter_grid_position_bottom, a row is
inserted. If side is clutter_grid_position_left of
clutter_grid_position_right, a column is inserted.
| this | |
| sibling |
the child of this that the new row or column will be placed next to |
| side |
the side of |