Handle http bind settings

For now, it's only possible to configure the listening port through the environment variable PORT.
It is not possible to select the binding address, nor the protocol to use. So, as a default, Node will bind to :: if IPV6 is available, else 0.0.0.0.

Add to new configuration settings to configure the port and bind adresse :

• http.port
• http.bind

These variables can be defined as environment variables, as any other. But to have an equivalent of the PORT envar, allows a BIND envar to define the bind address, which should have precedence over config and config's regular envar.