New feature: When solving a problem interactively it is now possible to mark "candidates" for cells. When printing, these candidates are printed also.
Corrected Bug: When calculating more than one solution for a problem, it happend in some cases that the displayed solution was marked as "invalid" even though it was a perfect solution for the given problem. This has been fixed.
Corrected Bug: When prining a problem it sometimes happend that not only the given problem but also some other (calculated) values in some cells were printed out. This has been fixed.
