Added cache for application settings (Setting model).

Once the values are cached, only one database query is done at each user request (to check if the cache is still valid).

git-svn-id: http://redmine.rubyforge.org/svn/trunk@685 e93f8b46-1217-0410-a6f0-8f06a7374b81

db/migrate/065_add_settings_updated_on.rb

@@ -0,0 +1,11 @@
+class AddSettingsUpdatedOn < ActiveRecord::Migration
+  def self.up
+    add_column :settings, :updated_on, :timestamp
+    # set updated_on
+    Setting.find(:all).each(&:save)
+  end
+
+  def self.down
+    remove_column :settings, :updated_on
+  end
+end