Checks if script is running as root, non-root, or sudo. For root, it sets SUDO variable to nothing and the script runs. If it's not root, then it checks to see if sudo is installed. If it is installed, then it sets SUDO variable to 'sudo' and the script runs. If it is not root and sudo is not installed, then the user does not have sufficient privileges to run the installer and it exits.
lighttpd in Jessie uses /var/www/html for the root folder, so in order
to only edit one lightpd.conf file, the installer will create the
correct directory even if not being run on Jessie.
Detects if the Pi had an original Pi-hole by looking for adList.conf.
If it exists, it backs up all the files to /etc/pihole/original. Then,
the script continues as normal and creates the new files. This helps
ensure that /etc/hosts and /etc/dnsmasq.d/adList.conf are not being
used simultaneously.
