Allow students to contribute to the wiki

There is now a matrice:
No Groups Separate Groups Visible Groups
Teacher Teacher creates and changes the wiki. Students can read the contents. There is a wiki for every group which just the teacher can change. Every student just sees the wiki of his group. There is a Wik for every group which just the teacher can change. The students can see all wikis, choseable by a Drop-Down box which contains all groups.
Course/Group Teacher and user can create and change the wiki. Students can change and see the wiki of their own group. Students can change the wiki of their own group. They can see all wikis, choseable by a Drop-Down box which contains all groups.
Student Every student sees and can change his own wiki. Every student can change his own wiki, and sees all other wikis of the students in his group, choseable by a Drop-Down box which contains all students of his group. Every student can change his own wiki, and sees all other wikis, choseable by a Drop-Down box which contains all students.