use csrf protection correctly, fixes #4545

app/controllers/admin/login_style.php

app/controllers/admin/user.php

app/controllers/contact.php

app/controllers/course/timesrooms.php

app/controllers/course/wiki.php

app/controllers/materialien/files.php

app/controllers/questionnaire.php

app/controllers/settings/deputies.php

app/controllers/shared/contacts.php

app/controllers/studiengaenge/studiengaenge.php

app/views/materialien/files/index.php

app/views/materialien/files/range.php

app/views/shared/contacts/index.php

lib/classes/forms/Form.php