Add node button to display next most specific ancestor for each child node

[shintoo]

E.g. if the tree is:

• Birds (aves)
  • Blue jay (cyanocitta cristata)
  • Common kingfisher (alcedo atthis)

Then there should be a button for the class Aves node that expands the tree into:

• Birds (aves)
  • Perching birds (passeriformes)
    • Blue jay (cyanocitta cristata)
  • Kingfishers and allies (coraciiformes)
    • Common kingfisher (alcedo atthis)

By doing something like the following:

function expand(node):
  for each child of node:
    addNode(child.ancestors.indexOf(node.id) - 1)) # Add the next lowest ancestor (e.g. pass. or cora.)