Fairly major commit. This will break the current version of ihost, but this
had to be done really to give Pete something to test the new ihost against.

The main change here is removal of the TCP Heartbeat functionality from the
filter. This meant the following features stopped working :-
  - Heartbeat testing
  - Configuration checking
  - Service checks

The heartbeat testing, specifically the monitor, now looks at the presence
of UDP packets instead. Before it just looked for the presence of a TCP
heartbeat packet, so the change their is fairly negligible. Of course this
means heartbeat testing now relies on the UDP working... but I don't see
this as a problem.

Configuration checking has been repositioned in to the filtermanager. This
is a backwards compatible change - the filtermanager should still perform
as it should for older hosts. But now there's an extra command to check the
configuration is up-to-date, with a similar format to the old TCP protocol
in the filter. (although we may optimise this soon)

The service checks are broken. This isn't a major issue for us as they were
pretty useless in the first place. The concept is good, but the checks are
just far too primitive. I expect at some point I'll work on a seperate
component that just monitors services, which will replace this function.

Further changes in the server include removal of the key checking code,
as this relied on a bolt on to the TCP heartbeat protocol to ship the
key. This got more akward than originally planned, so I'm happy to drop the
idea. In the long term we hope to replace this with a public key systems
for signing and even encryption.

Finally, general tidy up to remove other bits of code that check for
TCP heartbeat packets when they don't need to any more.