Allow selection of non-editable text

[martinmcclure]

Morphic labels and other non-editable text is not selectable by default in Pharo.
It would increase usability to be able to select and copy (using hot-key) most text in a Sparkle explorer.

Paragraph text can currently be selected and copied even when not editable, but no insertion bar shows. It would be better to have some kind of visual feedback of selection position, but probably not an insertion bar.

[martinmcclure]

One idea is to allow selection highlighting of non-editable text, but highlight very differently (different color, or select by underlining and/or overlining, outlining in a selection box, etc.)