Updated InteractiveViewer Widget for Graph Exploration

[zwelz3]

For users trying to visualize RDF graphs, there are two major challenges:

1. Reducing the graph to a subset of information that is small enough to inspect
2. Interacting with the graph in order to identify and isolate relevant information

#98 is an attempt to provide users with a way to incrementally explore the RDF graph as a LPG. However, due to limitations of the graph visualization library ipycytoscape, that work is delayed.

This ticket scopes an interim capability to identify relevant information and allow users to inspect portions of a sub-graph.

The capabilities of this visualization:

• coloring graph nodes by rdf:type
• ability to toggle on/off nodes by rdf:type
• scalable graph layouts (e.g., spacing factor)
• Improved resilience of cytoscape-based widgets