Value axis zoom with scroll-wheel

[john-haugland]

Currently the scroll-wheel will zoom the y-axis (depth) centered around the mouse pointer. We also need to zoom the x-axis (value) around the mouse pointer. Suggestion is to hold shift key as key modifier while using the scroll-wheel. Also x-axis zoom should be possible without key modifier if hovering over the value-axis screen area while using the scroll-wheel. This is standard behavior in several other plotting libraries.