Cosmetic: expand the clickable area of the new rule dialog checkboxes

[dca00]

Would it be at all possible, to expand the new rule dialog checkbox clickable areas, to cover their labels as well?
If Qt allows that, it would make the dialog more user-friendly, by simplifying the clicking of the checkboxes.

[gustavo-iniguez-goya]

Added finally. This feature was requested in #865 , and I've found an easy way to do it.