- Converted the constraints of type building(s) min one activity in each non-break time slot to the similar constraints of type building(s) min one activity in each available time slot (suggested by Benahmed Abdelkrim). Also, these constraints must no longer be applied to all the buildings, but can be applied to any selection of buildings (again, suggested by Benahmed Abdelkrim). - Added some tests before the generation, if the timetable is impossible because of the constraints of type building(s) min one activity in each available time slot (suggested by Benahmed Abdelkrim). - Minor code improvements. - Corrected the Arabic translation, by Benahmed Abdelkrim.