Fire: Rewrite fire sound code

Previous code:
Used looped sounds without attaching them to objects or playing direct
to players.
The looped sounds are not 'stopped' when players leave the area.
These may be causing the bug where sounds are heard at extreme
distances.
Entering a world with already present flames results in silent flames.
Sounds are often played at a large number of points in a 6 node lattice.
A large fire is reported to cause a high load, disabling the sound code
is reported to help this.

New code:
Optional flame sound to not interfere with ambience mods.
Permanent flame now has sound.
For multiple flames, sound is positioned at the centre of all flames, and
has volume determined by flame number.
The original freesound 'large fire' recording was used to create 3 sounds
that play at random for a non-repetitive effect. At low volume it is
suitable for small fires.

Original sound files and sound function (as an empty function) kept
temporarily to reduce disruption.

Reduce gain of flame extinguish sound.