tdt: ignore other network in NIT this causes havoc with DVB-S networks.

This is particularly true where the other network is only available
via another orbital position (we could check for this) but it also
causes problems with other transmission types so I think we'll just
ignore for now.
tdt: some changes to SDT processing to pick up unknown services
services: include info from SDT (for Other services) if they already exist.

Services can be added from a variety of other tables which probably indicates
that they are in fact valid TV/Radio services, but we just don't know the
type.

This might help people to map these services manually within TVH.
dvb: attempt to stop bad updates to network info.
tvhlog: some efficiency improvements
tvhlog: fix some problems with hexdump code
dvb: add some additional tracing into NIT/SDT parsing