SPARQLgraph ingestion bug fix

Fixed a new and potentially serious bug in SPARQLgraph that caused the nodegroup json for import specs to be written improperly when there was a URILookup to a node whose name had been changed from the default.
This affects ingestion performed through SPARQLgraph using existing templates, as well as the creation of new import templates.

It does not affect python or service layer ingestion. It also does not affect ingestion performed in SPARQLgraph by dragging the nodegroup into the mapping tab (instead of the "normal" query tab).

For RACK 4

Some minor bug fixes and improvements for RACK 4 release

SPARQLgraph nodegroup-loading bug fix

Fixed a rather serious new bug affecting loading of nodegroups into SPARQLgraph.
Assorted minor improvements.

Union query & ingestion bug fix

Fix where union query work had introduced a bug into ingestion.

Union queries integration testing 2

Made significant improvements and bug fixes to SPARQLgraph UI related to union queries.
Most notably: combination of UNION and MINUS in same clause.

SemTK Snapshot v2.3.0-20201103

This is SemTK snapshot v2.3.0-20201103.