CRM-13213 : updated joomla cms code for fetching UF locale

In joomla 3.1, JFactory config method <code>$conf->getValue('config.language');</code> is no longer in use.

So, to maintain joomla 2.5.x / 3.x compatibility :  <code>$conf->get('language')</code> method is used. 

Joomla cms usage of the same method can be seen in : <code>joomla-root/libraries/joomla/factory.php</code> (did some modifications to the patch submitted WRT to this).