plumb URDF/SDF audio_source into PhysicsServerCommandProcessor, allow to play sounds on collision !

See also https://youtu.be/eppOjTfx5Jg for a first test, and this modified URDF how to add sounds:
https://github.com/bulletphysics/bullet3/blob/master/data/plane_with_collision_audio.urdf
Add the --audio flag to enable sound in pybullet/Bullet-C-API

src/BulletCollision/CollisionDispatch/btCollisionObject.h

@@ -140,6 +140,7 @@ public:
 		CF_HAS_CONTACT_STIFFNESS_DAMPING = 128,
 		CF_HAS_CUSTOM_DEBUG_RENDERING_COLOR = 256,
 		CF_HAS_FRICTION_ANCHOR = 512,
+		CF_HAS_COLLISION_SOUND_TRIGGER = 1024
 	};
 
 	enum	CollisionObjectTypes