Add average working time to exercise statistics

app/views/exercises/statistics.html.slim

@@ -8,6 +8,9 @@ h1 = @exercise
   p == @exercise.average_score ? t('shared.out_of', maximum_value: @exercise.maximum_score, value: @exercise.average_score.round(2)) : empty
   p = progress_bar(@exercise.average_percentage)
 
+= row(label: '.average_worktime') do
+  p = @exercise.average_working_time
+
 - Hash[:internal_users => t('.internal_users'), :external_users => t('.external_users')].each_pair do |symbol, label|
   strong = label
   .table-responsive

config/locales/de.yml

@@ -248,6 +248,7 @@ de:
       score: Punktzahl
       runs: Versuche
       worktime: Arbeitszeit
+      average_worktime: Durchschnittliche Arbeitszeit
       internal_users: Interne Nutzer
       external_user: Externe Nutzer
     submit:

config/locales/en.yml

@@ -171,7 +171,7 @@ en:
       exercise: Exercise
       score: Average Score
       runs: Average Number of Runs
-      worktime: Average Worktime
+      worktime: Average Working Time
   exercises:
     editor:
       confirm_start_over: Do you really want to start over?
@@ -247,7 +247,8 @@ en:
       user: User
       score: Score
       runs: Runs
-      worktime: Worktime
+      worktime: Working Time
+      average_worktime: Average Working Time
       internal_users: Internal Users
       external_users: External Users
     submit: