Update

1. Fixed wrong GraphComment placement in scene (it was trying to place
it twice).
2. Changed GraphVisEdge behaviour. Now it has itemchange(), you can
select it and see that it is selected. It processes geometrychanges of
it's nodes and changes it's coordinates. Also, updated painterpath so
that you can select it (by dragging the selection bound)
3. GraphVisNode now calles edges to refresh their properties when one
moved. It costs some in perfomance.
4. Added actionEdit for the future (triggering it will call an editor of
selected item).
5. Connect button will connect two nodes no matter what else is
selected.