Re-applied "Graph layout optimizations"

[fbarl]

Brings back the reverted changes from #2128 and introduces a fix for node labels rendering on Firefox.

[foot]

LGTM!

• Default zoom for small layouts (e.g. 2-3 nodes) is very high. I understand the zoom is set so that the nodes fit + 10% border. This works great for large layouts. Too accomodate smaller ones we could perhaps Math.min(calculatedZoomWith10%Border, aNiceAestheticNodeZoom);

[fbarl]

@foot, I did the change you proposed, essentially with aNiceAestheticNodeZoom = maxZoomScale / 2 and it does look better :)