Please document dynamic in proxy server section in proxy.conf

[Sam Hartman]

If you're looking at designing dynamic realms here are the parts we use
that might not be preserved in all designs:


* Being able to dynamically specify  tls information

* Per Alan's recommendation, being able to have home servers that are
  not part of the standard rbtrees, so we can avoid a security exposure.
  If two realms claim to be served by a server with IP address
  192.0.2.23, we don't want one of these realms to be able to overwrite
  the key for the other.  Either both keys will work for the same IP
  address, or someone is being dishonest, but it's important not to
  combine home servers in this instance just because they have the same
  IP and hostname

* Being able to have the over-the-wire realm name different  than the
  internal representation.  (The suffix of the user-name attribute ends
  up not being the same as the realm name returned)

* Being able to evaluate periodically with access to connection stats
  for the home servers whether a realm is still good or whether we want
  to dynamically  contact it again