cytoscape-impl

Checking parts before importing to remove NullPointerException.

Modified type detection when importing Excel files.

Merge remote-tracking branch 'origin/develop' into develop

Merge branch 'develop' of github.com:cytoscape/cytoscape-impl into develop

CYTOSCAPE-12532 #comment Just changes Visual Property label from "Node Label Drag & Drop" to "Node Label Selection", because that's what it is called in the corresponding View toolbar button (tooltip).