Now, there is nothing that can react to `set_...()` calls, so
offering this possibility can cause wrong assumptions as to what one
can do as soon as a WebServer instance has launched.
The main program can still decide whether to supply the optional
credentials or not, but this way, the configuration can become a Value
Object that won't change after initial creation.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
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.
