Cleanup of clusters in argus view.
Cleanup of clusters in argus view.

First set of changes enforces our minimum cluster size in all cases,
which addresses #1138. Second set of changes makes sure that extra-wide
labels get a wide-enough highlight (appears on mouseover), see for
example [the 'uncultured'
node](https://devtree.opentreeoflife.org/opentree/argus/opentree10.2@ott5248879/uncultured)
on **devtree**.

OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree,OpenTreeOfLife/opentree