Zoom during rod endpoint updating

[a-niem]

The following problem was elaborated by @KirstenHarth :

During the updating of rod endpoints one wants to be as precise as possible. This often requires zooming into the image.
Currently this is a bit tedious, because during zooming the upper left corner is fixed and ROIs might be zoomed out of the view.
An improvement could be to automatically zoom to an area around the first selected endpoint, similar to that in the old version of this program coded in MATLAB.

Another solution could be to have a magnifying region around the cursor:
a) permanently
b) after the first endpoint selection
c) toggleable with a keyboard shortcut

A third solution could be always zoom towards the cursor, similar to how many CAD programs are operated.