CoeSwd9: Various QTreeView features
Bug Number: n/a
Release notes (y/n): no
For Release Nums: 7.1

(1) Fixed "Graph (row,col)" column values.

(2) Corrected value display for Markers (but we're putting Marker support 
  aside).

(3) Enable/Disable Items, by Item Type (Plot, Curve, etc.) based on Edit Mode.

(4) Incell label editing for Plots and Curves, initiated via:
  (a) double clicking cell.
  (b) context menu operation: "Edit Label".

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