* Correct sorting in table
* Modify page when nested in exercises
* Fix links between pages
* Link from statistics page to programming_groups/index
* Link from submission page to programming_groups/<id>
* Allow filtering for exercise ID on ProgrammingGroup#index
* Add search fields for internal and external user id on pg/index
Further, we remove the "check invitation" button and extract some methods to our new ProgrammingGroups object in JavaScript.
Co-authored-by: Sebastian Serth <Sebastian.Serth@hpi.de>