reduce unneeded vertical tree spacing

[westram]

When changing font sizes for different color/font definitions (GCs), arb automatically resizes the vertical distances in the dendrogram view.

If using different sizes e.g. for marked and unmarked species and/or groups (as shown in the attached picture), a more condensed view would be possible, if the vertical distance between species shown in smaller fonts, could be reduced.

Currently arb detects the biggest potential font and uses its size for all distances.

---

related: #706

[westram]

arb screenshot showing unwanted vertical spacing

[westram]

Different font sizes configured and current effect on display: