Merge remote-tracking branch 'origin/master' into error-info

# Conflicts:
#	app/controllers/concerns/submission_scoring.rb
#	app/views/application/_navigation.html.slim
#	config/locales/de.yml
#	config/locales/en.yml
#	db/schema.rb

app/policies/comment_policy.rb

@@ -12,14 +12,10 @@ class CommentPolicy < ApplicationPolicy
     everyone
   end
 
-  [:new?, :destroy?, :update?].each do |action|
+  [:new?, :destroy?, :update?, :edit?].each do |action|
     define_method(action) { admin? || author? }
   end
 
-  def edit?
-    admin?
-  end
-
   def index?
     everyone
   end

app/policies/exercise_collection_policy.rb

@@ -0,0 +1,3 @@
+class ExerciseCollectionPolicy < AdminOnlyPolicy
+
+end

app/policies/subscription_policy.rb

@@ -0,0 +1,18 @@
+class SubscriptionPolicy < ApplicationPolicy
+  def create?
+    everyone
+  end
+
+  def destroy?
+    author? || admin?
+  end
+
+  def show_error?
+    everyone
+  end
+
+  def author?
+    @user == @record.user
+  end
+  private :author?
+end