Improve acsf-uninstall command

When running acsf-uninstall command and answering yes to all the questions, the command leaves some empty directories and an empty settings.php.

It should check if hooks/ sub-directories still contain some files and delete these if empty. Finally delete the hooks/ directory if empty.
It should check if sites/g/ is empty and delete if so.
It should either delete the sites/default/settings.php file or copy the content of sites/default/default.settings.php.