Add using Piwik\Common

Following error:
PHP Fatal error:  Class 'Piwik\\Tracker\\Common' not found in /var/www/piwik/core/Tracker/ActionClickUrl.php on line 43
Remove unused libs
Revert "Add using Piwik\Common"

This reverts commit 91970b0df8e8e9393733db9ea84e02f03177bea8.
re
Merge pull request #167 from pebosi/remove_libs

Remove old lib directories when updating from 1.12 -- thanks for fixing the namespace bug too!