Refactor scripts enabling direct execution by user www-data

[martignoni]

Idea: get rid of current complicated way to run root-only commands via cron.

How: enable some carefully chosen commands to be run by user www-data using sudo. This involves enabling some commands in /etc/sudoers file, e.g.

www-data ALL=(ALL) NOPASSWD:/usr/sbin/reboot

[martignoni]

Create new sudoers file and add there the selected commands.

sudo visudo -f /etc/sudoers.d/020_www-data-nopasswd