adds activity page to administration

app/controllers/admin/activity_controller.rb

@@ -0,0 +1,8 @@
+class Admin::ActivityController < Admin::BaseController
+  has_filters %w{all on_users on_proposals on_debates on_comments}
+
+  def show
+    @activity = Activity.for_render.send(@current_filter).order(created_at: :desc).page(params[:page])
+  end
+
+end