Moving around in graph view and design view on laptop

[PiispaH]

In #2561 the controls for making selections were redone. Because of the changes, moving around using only a laptop trackpad requires one to use the scroll bars. Maybe if some button like ctrl was pressed down, the views could be scrolled through by dragging with the left mouse button?

[soininen]

The natural way of panning the view on touchpad would be to use two-finger scrolling. We should look into enabling that.