anonymous: new AccessControl category

anonymous is evaluated after configured / unconfigured but before
authenticated / unauthenticated.

Use anonymouse to configure entries for both a non configured server and
unauthenticated users in a configured server. This allows to add and
test this entries before settling on the configuration of the server.
anonymous, unconfigured and configured by default

Added anonymous, unconfigured and configured by default so people don't
miss them.