* Hide non-public exercises and proxy exercises
* Hide average working time value on statistic page
* Add hint about filter to submission page for teachers
* Hide display name from feedback page
Tags can be added to exercises in the edit view. Tags can monitored under /tags.
Added the concept of ProxyExercises which are a collection of Exercises. They can be found under /proxy_exercises
Added Interventions as prework to show interventions later to the user.
Added exercise/[:id]/working_time to return the working time of the user in this exercise and the average working time of all users in this exercise
