Principal assistant role

[mytja]

• [x] Sees everything that a teacher sees (without a class)
• [x] Sees data about all employees and students
• [x] Creates, edits and deletes classes, subjects, users
• [x] Assigns roles to users (lower roles than own)
• [x] Can manage teacher absences (nadomeščanja)
• [x] Can be multiple persons, though it's recommended to have only one person with this role

[mytja]

Done. pushing soon