MgDevHttpServer: Support optional host to listen on

[jng]

MgDevHttpServer is currently hard-coded to always listen on "localhost". While this is generally the safe and correct setting, it does hamper its usability when run inside a docker container, where you want to bind on "0.0.0.0" to be accessible outside the docker container.

To support this, MgDevHttpServer should support an optional --host parameter that controls what host the http server will listen on. If not specified, it will assume the default value of "localhost"

[jng]

In 10091:

Allow customizable hostname/IP for MgDevHttpServer to bind to via a new (and optional) --bind-to/-b parameter

Fixes #2881