SID for IP autoconf

[braice]

I'm streaming a lot of channels with auto configuration,
and when a channel was removed, I had to resort to start mumudvb with the old generated config,
to have fixed ip addresses for my STBs.
I could have rewritten the config as partial auto configuration as well, but this still leaves something to be desired.

There for when working on auto configuration of ip addresses, please include the possibility to use
SID (in low and high byte variables) like this autoconf_ip4=239.0.%SID_hi.%SID_lo
maybe also TID, since this would help creating unique IPs.

[braice]

Done !