Fix functions naming for both Commerce Kickstart versions install.
Make sure that Bind9 DNS Server is re-installed properly if removed because of conflicts during system upgrade.
Use full paths when replacing config files.
Do not add and remove bind from /etc/sudoers since it is not supported.
Allow to specify extra packages to install and protect with _EXTRA_PACKAGES option.

Useful to specify packages not included by default which could be otherwise removed because of some conflicts due to the aggressive Barracuda behaviour: apt-get autoremove -y