Feature/caddy frontend haproxy
Important notes:
- 
mpm-graceful-shutdown-timeoutparameter is dropped, as it's considered unused in context of CDN deployment - 
Content-Typeis not modified at all - so in case if backend sends nothing, nothing will be added (previously Caddy tried to guessContent-Type) - websocket is enabled by default on all slaves and 
type:websocketis required only to usewebsocket-path-listandwebsocket-transparentoptions