Forum index improvements and more

+ option to add forum category description
+ option to show last user post avatar in forum
+ added global.css which will contain css rules that will help keeping
compt. with older themes
* forum index was reformated to be a bit more semantic and added more
css classes
* jscript.js has been beautyfied in order to facilitate further
modififications

There is still room for improvement on forum index and other forum pages will also be reformatted when will have enough time.