Out Canv: Migration of OutputCanvasScene to OutputCanvasGfxItemMgr [1]
Bug Number: n/a
Release notes (y/n): no
For Release Nums: 7.1

First step in migration of QtUtils/OutputCanvasScene (a QGraphicsScene) 
to new class, OutputCanvasGfxItemMgr.

This commit introduces OutputCanvasGfxItemMgr as a QGraphicsScene.  
It will be migrated to being just a QObject.  And the OutputCanvasScene 
will delegate to this new class.

This builds and runs, but the OutputCanvasGfxItemMgr is not yet used.

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