Replace occurences of `url_for('/...')` with appropriate `action_url()`

app/controllers/admin/overlapping.php

app/controllers/course/admission.php

app/controllers/course/dates.php

app/controllers/course/enrolment.php

app/controllers/course/lvgselector.php

app/controllers/course/management.php

app/controllers/course/plus.php

app/controllers/fachabschluss/abschluesse.php

app/controllers/fachabschluss/faecher.php

app/controllers/fachabschluss/kategorien.php

app/controllers/lvgruppen/lvgruppen.php

app/controllers/materialien/files.php

app/controllers/module/institute.php

app/controllers/module/module.php

app/controllers/room_management/overview.php

app/controllers/search/angebot.php

app/controllers/search/module.php

app/controllers/search/studiengaenge.php

app/controllers/shared/contacts.php

app/controllers/studiengaenge/informationen.php