Note: This is adaptation of apache-frontend

ACHIEVEMENT UNLOCKED: Requesting working instance to any simple redirect
                      like backend (like Webrunner).

Features:

 * added a lot of bugs
 * simple, Webrunner like, backends are supported
 * buildout templates are named by their usage in instance buildout (master,
   slave)
 * file templates names are minimised and try to express functionality
 * follows Caddy per-instance self-contained configuration
 * redirection from http to https
 * annotated slave buildout with readable part names
 * comptability with software/erp5testnode/testsuite/ infrastructure
 * same request parameters as for apache-frontend are supported

Caddy executed with:

 * disabled automatic SSL
 * pidfile location
 * log location
 * specified http and https ports
 * site root

Slave improvements:

 * SSL files are in each slave configuration
 * same for IPv4 and IPV6 information
 * pass proper variables to slave list
 * remove not needed varfiables from slave list
 * per-slave SSL certificates supported
   This seems to be hacky, there is need to clean up the whole infrastructure,
   to follow Caddy per-instance self-containment approach.