Add Apache module list to ?do=debug information

This should make it possible to see if mod_security is involved,
at least on servers running mod_php.
Merge pull request #542 from splitbrain/debug_apache

Add Apache module list to ?do=debug information
enable/disable extensions via AJAX FS#2927
move geshi highlighting to it's own LESS file
recompiled geshi styles FS#2902
combined geshi styles

using http://cleancss.com/
LESSified GeSHI styles
removed Yahoo sitemap ping, added Yandex instead FS#2880