Implement automatic bootstrap using Avahi.

Policy server can be discovered over Zeroconf protocol using Avahi.

Avahi is discovered at runtime using dlopen.

Implemented new command line option for cf-serverd: -A. With this option
cf-serverd generates avahi configuration file in /etc/avahi/service and
restarts avahi-daemon.

cf-agent will look for policy server if only --bootstrap/-B option is
passed without an IP address. If multiple servers are found cf-agent
will print list with hostnames and IP addrresses and ask user to run
cf-agent --bootstrap --policy-server <rigth IP address>. If no server is
discovered cf-agent will exit normaly.