Add support for chrooting Apache and suEXEC

See:

• https://httpd.apache.org/docs/2.4/mod/mod_unixd.html#chrootdir
• https://httpd.apache.org/docs/2.4/mod/mod_suexec.html#suexecusergroup
• https://httpd.apache.org/docs/2.4/suexec.html
• https://www.howtoforge.com/tutorial/chrooting-apache-2.4-with-mod_unixd-on-debian-8-jessie/