Insert/remove vertical space on page. Implemented new pen "Insert Pen".

[QubaB]

Implemented new pen "Insert Pen". When stroke is created using this pen, all items on page below first point of stroke are moved up/down by the vertical length of stroke.

Can be used to create free vertical space on page (or remove it).

When moved items do not fit to page, its height is enlarged to hold all items

Solves #1455