director: Added "authreply" socket type. This allows defining a socket, which receives auth replies. Director then adds the "host" field to it if it's missing and returns back the original string. The idea is that eventually a director ring could be running independently from Dovecot proxies.

director: Added support for LMTP proxying. --HG-- branch : HEAD

Added initial implementation of a director process (for NFS users). There are still some unimplemented features and bugs. Also changing mail server list doesn't yet make sure that other directors won't assign the same user to a different server at the same time. --HG-- branch : HEAD