Speakers now play sounds using a custom set of packets.
- When playing a sound, we send the resource id, position, volume,
pitch and a UUID for the _speaker_ to all nearby clients.
- This UUID is then used when we need to update the sound. When the
speaker is moved or destroyed, we send a new packet to clients and
update accordingly.
This does have one side effect, that speakers can now only play one
sound at a time. I think this is accceptable - otherwise it's possible
to spam ward in a loop.
Notes still use the old networking code, and so will not be affected.
Closes#823
Jonathan Coates