New feature for Statuses

New feature for statuses. It gives the possibility to specify (with a checkbox in add/edit statuses page) for a status, e.g., saved as “Justified”, to not combine to the total of presences/absences. This feature is related to the percentage one. If a student must have a minimum percentage of 60% to access final exam, and in a total of six lessons his report is P-A-P-J-P-A, if status J is like A, without the new feature, the percentage would be 3P/6 = 50%, in the other case (with feature and Grade set to 0) would be 3P/5 = 60%.
In addition, this feature could be useful also to gain Grades in extra lessons. If this feature is selected for a status (E) with e.g. Grade set to 1, attending a lesson with status E means make own percentage grows.