Refactor post_approvers_only to approver_only.

Don't duplicate code with post_approvers_only; use the approver_only?
method dynamically defined in `User::Roles.each do ... end`.

app/controllers/application_controller.rb

@@ -174,13 +174,4 @@ protected
       Rails.application.config.session_store :cookie_store, :key => '_danbooru_session', :secure => false
     end
   end
-
-  def post_approvers_only
-    if CurrentUser.can_approve_posts?
-      true
-    else
-      access_denied()
-      false
-    end
-  end
 end

app/controllers/moderator/post/approvals_controller.rb

@@ -1,7 +1,7 @@
 module Moderator
   module Post
     class ApprovalsController < ApplicationController
-      before_filter :post_approvers_only
+      before_filter :approver_only
 
       def create
         cookies.permanent[:moderated] = Time.now.to_i

app/controllers/moderator/post/disapprovals_controller.rb

@@ -1,7 +1,7 @@
 module Moderator
   module Post
     class DisapprovalsController < ApplicationController
-      before_filter :post_approvers_only
+      before_filter :approver_only
 
       def create
         cookies.permanent[:moderated] = Time.now.to_i

app/controllers/moderator/post/posts_controller.rb

@@ -1,7 +1,7 @@
 module Moderator
   module Post
     class PostsController < ApplicationController
-      before_filter :post_approvers_only, :only => [:delete, :undelete, :move_favorites, :ban, :unban, :confirm_delete, :confirm_move_favorites, :confirm_ban]
+      before_filter :approver_only, :only => [:delete, :undelete, :move_favorites, :ban, :unban, :confirm_delete, :confirm_move_favorites, :confirm_ban]
       before_filter :admin_only, :only => [:expunge]
       rescue_from ::PostFlag::Error, ::Post::ApprovalError, :with => :rescue_exception
 

app/controllers/moderator/post/queues_controller.rb

@@ -2,7 +2,7 @@ module Moderator
   module Post
     class QueuesController < ApplicationController
       respond_to :html, :json
-      before_filter :post_approvers_only
+      before_filter :approver_only
 
       def show
         cookies.permanent[:moderated] = Time.now.to_i

app/models/user.rb

@@ -430,6 +430,10 @@ class User < ActiveRecord::Base
       is_gold? || is_super_voter?
     end
 
+    def is_approver?
+      can_approve_posts?
+    end
+
     def create_mod_action
       if level_changed?
         ModAction.create(:description => %{"#{name}":/users/#{id} level changed #{level_string_was} -> #{level_string}})