Limit HTTP proxy listen address + add real_ip_header config option

[ptrsvbd]

The HTTP proxy should respect IPv4 address set in configuration and not listen on 0.0.0.0 so it won't interfere with other daemons listening on the same port on different (specific) IP address.

When Evilginx is running behind a reverse HTTP proxy, the information on client IP address is lost. The client with IP address A.A.A.A connects to proxy at B.B.B.B, which then makes connection to Evilginx at C.C.C.C. The client IP address in Evilginx is determined from source address of the TCP connection and so B.B.B.B is logged and used in blacklist instead of A.A.A.A. The new config option real_ip_header adds possibility to read information on original client IP address from a specified HTTP header set by the reverse HTTP proxy (e.g. "X-Forwarded-For")