Updates to course & class statistics

• Course statistics optimized: Large statistics are loaded faster now
• Students > General tab (in many population views): Studyprogramme-column does not show non-degree programmes anymore
• Activity status for rare studyrights (specializations in medicine, dentistry & veterinary) are determined differently now: No term registrations required, only validity dates are taken into account
• Evaluation overview: Better error message when link has a nonexistent faculty

Internal

• Updater: minor improvements to handling errors