Scrolling with mouse wheel is not smooth

[tahini]

In a typical application, scrolling down with mouse wheel with one full finger strike makes the page scroll down around 1/3 of the page, so that after 3 strikes, the page is completely new. In the timeline-chart, a full finger strike scrolls down barely a line. So it takes a lot of finger work to scroll down a full page!

[tahini]

Maybe related to this, but zooming with the mouse wheel also does not zoom very fast (compared with say, zooming with W/S when PR #25 is merged)

[PatrickTasse]

I see that one mouse wheel click down moves the graph down by about 3 time graph rows, which is the same I observe in Eclipse TC.

For the horizontal (time) zooming it should be fixed with #114.