First attempt to list markup output
More stable Markup - still ugly
Simplify setting default renderer
Renderer orks and does updates correctly.
Adjusted cell sizes
Works better now - with a combined CellEditor and Renderer.
Still need to fix: 

new Panel
tab does not work anymore to give editable focus
Panel and Label only created once now.
Separated CellEditor and CellWrapper into their own files.
Cleanup and helpful comment
Added solved message
Now with working cursor keys. Just need to sort out readonly fields.
Moving cursor works now (except for one funny case)

If leftmost column is read-only and the cursor is moved left,
nothing happens.
When solved, make all cells read-only.