via CLetterMatrixResultsLineDelegate.
Define values for the UserRole enum extensions for model data() of
CELSResultListModel and CLetterMatrixTableModel.
Add metatypes for CELSResultList and CELSResultSet.
Add UserRole_ResultsSet to get results for a specific index of
CLetterMatrixTableModel.
The problem with this implementation is that the per-item delegate
has to draw across other items, which makes for update and paint
ordering problems. This needs to be replaced by some sort of pixmap
overlay and painted by the view itself overtop of the viewport.