added possibility to add/delete points in/from shape

operation does not support undo/redo
opertion available in DRAG mode only

to add point - press and hold left mouse button in some place of canvas
and press F4
if place is clear - new point will be added to last drawed shape
if place is on the shape - new point will be added to selected shape

to delete point - press and hold left mouse button on some point of any
shape on canvas and press F4. Confirm.