Improve display of branch-based phyloreferences

[gaurav]

We currently display all phyloreferences as originating on a note and including all of its descendants, but this is not technically correct, because branch-based phyloreferences should extend up to the previous node (but not include it). Actually drawing this will be technically difficult, so we'll leave this for a future version.

Some ideas from #315:

• For branch-based phyloreference, we could add a symbol to the clade, and then add a note underneath the phylogeny to say that this is clade extends up the parent branch.
  • Note that qualifiers can render a node-based clade into a branch-based clade, so we might want to look for "maximum" or other text in the definition.