Remove the regovar user from the sudoers

[Oodnadatta]

Use root to install and configure Regovar (https://github.com/REGOVAR/Regovar/blob/master/install/install.sh) and the regovar user for everything else. It would be safer not to have the regovar user in the sudoers list.

Idea 1 which is easier:

• the install.sh script must be run by a sudoer;
• it asks for the name of the regovar user;
• it uses sudo as it currently does for operations which must be done as root;
• it uses sudo -u $regovar_user_name for operations which must be done as the regovar user.

Idea 2 which is better:

• complete dockerisation of Regovar (with no change to the host: without writing in /var/regovar and using nginx in the container).