This enables the WebServer to run protected by a username and password.
While it isn't possible to access such a protected server from inside
Serenity as of now (because neither the Browser nor pro(1) support
this), this may very well be the case in the future. :^)
This moves the configuration of the web server, which currently only
consists of the root path, into a new class, Configuration. Since the
configuration is global and not per client, it is accessed by a
singleton getter.
This change simplifies future extensions of the configurable parameters.