Reworked the spatial sound playing algorithm.

- To avoid spamming sounds with setPosition()
- And add sound culling handling.

Now only sounds near you point of view will be heard.
I also made it so if you you go higher, you can hear more far away sounds...

Main part of #147
Reimported the ingame battle music to make it longer and actually loopable.
Made the fighting music also triggered when one of your allies is attacked.

Part of #147
Turned the playDespositGold server message into a more generic one.

Part of #147
Made the battle music start when one player's trap triggers.

Final part of #147
Added a missing assert in the sound manager, as requested by @hwoarangmy
Merge pull request #253 from Bertram25/sound

Reworked the spatial sound playing algorithm.