when doubleclicking on a cell which is not the active one AND that cell is not editable, then treat the doubleclick as a singleclick, i.e. set focus to the clicked cell anyhow (tested on: examples/example-custom-column-value-extractor.html).

Without this 'doubleclick downgrades to single click behaviour when cell is non-editable' focus/cell activiation behaviour is 'weird' as the doublecheck doesn't seem to do anything, while the obvious response is to activate the cell.