ResourcesConfigWindow: can save and load Ogre configs to ogre.cfg file

There are problems with the display frequency, see MantisBT issue #344
(http://cordobazombie.com.ar/dev/tracker/view.php?id=344)
Besides the OpenAL sound device configuration hasn't been implemented yet, see
MantisBT issue #345 (http://cordobazombie.com.ar/dev/tracker/view.php?id=345)