Add blur and pulsing effect to highlighted node.
Add blur and pulsing effect to highlighted node.

This should make it easier to spot the highlight in large trees. Note
that this also means we'll add non-breaking spaces to empty node labels,
so that they are big enough to show the highlight effect.

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