Moved the ability to switch off caddy's api access to variables not
intended to be overwritten. It still can, but it is much more difficult.
Since every docker deployment relies on caddy's api to be accessible it
seems weird to present an easily reachable option to turn it off
globally.
Added caddy as swarm container. Uses templated Caddyfile which can be
set up for testing purposes for now.
Depends on docker and docker-swarm, and will keep its stuff where
docker-swarm sets itself up.
