Make manual pencil marks more sane #2
Description
Currently, manual pencil marks works inverted, by default all values are possible and displayed. For convenience reasons it should work the other way around: no pencil marks are visible at first, and the user can select which ones shall be displayed.
The reason for this odd behavior is because manual pencil marks are simulated using the excludedValues property of each cell. This should be completely separated, the UI should take care of manual pencil marks as the stored values in the model are only needed for the hint solvers.