abstract out knowledge model so HuViz subclasses can parallel the modelling hierarchy

[smurp]

HuViz should better embrace its potential as a generic graph visualization framework.

Framing and Terminology

HuViz visualizes some ABox (assertion box) data -- which become the nodes in the graph -- in the context of a TBox (terminology box) data -- which become the hierarchies displayed in the class picker and edge picker. Currently

Motivation

There is call to be able to gracefully transition from viewing data based on its OWL ontology to visualizing that ontology itself in the context of the ontology for OWL itself.

Knowledge Model Hierarchy

NodeEdge Model aka Graph Model
┣━ RDF
┃   ┣━ OWL 
┃   ┃   ┣━ Orlando Ontology
┃   ┃   ┣━ CWRC Ontology
┃   ┃   ┣━ SKOS
┃   ┃   ┗━ (other random OWL ontologies)
┃   ┗━ RDFS
┣━ OKBC
┣━ KIF
┣━ TopicMaps
┣━ Mind Maps
┣━ State Transition Model
┣━ JSON
┣━ SQL (DDL as TBox, DML as ABox)
┗━ (other knowledge modelling frameworks)