Update model for storing additional node properties on phylogeny nodes

[gaurav]

We currently have a simple system that allows taxonomic units to be listed for named nodes on a phylogeny. Each phylogeny has an additionalNodeProperties dictionary, which maps node labels to dictionaries containing properties like expectedPhyloreferenceNamed and representsTaxonomicUnits. When the JSON-LD file is generated, these properties are copied into the cdao:Node entity having that node label on that phylogeny. phyx.js also uses these taxonomic units to carry out specifier matching.

The expectedPhyloreferenceNamed property is controlled by the "Expected nodes" field in the Curation Tool, which works fairly intuitively. However, the representsTaxonomicUnits property is controlled by clicking on labeled nodes on the phylogeny and choosing "Edit taxonomic units" in the popup menu. There is no comprehensive list of taxonomic units associated with nodes, or the evidence on the basis of which that determination is made. Furthermore, our current system only supports asserting that a node represents one or more taxonomic units; we would like to support additional relationships between taxonomic units as well (#129).

We need to update this model to include:

• the taxonomic unit represented by the node
• relationships between this taxonomic and another taxonomic unit, including:
  • the other taxonomic unit
  • the relationship between the two taxonomic units
  • an explanation of the evidence for this relationship
  • citations supporting this relationship

[gaurav]

I think this is overly complex for our needs, and can be replaced with a simpler implementation described in #228.

[gaurav]

We have agreed on the simpler solution mentioned in the previous comment, and so I'll remove this from the Klados v1.0 milestone.