Update to ammunition

Added 7.62 calibre ammunition (no weapon for it yet).

Added 6 new ammunition types:
Flechette: shotgun darts, high bleed, low KO
Homemade Buckshot: cheap, high bleed, low KO
5.56 Tracer: lights up when fired
5.56 HP: bad penetration, good everything else
.357 Tracer: lights up when fired
7.62: planned for a 7.62 AK rifle

Added comments explaining weapon and ammo definition parameters.

Added Penetration property to ammo types. This value determines how
effective the round is against armour. More is planned such as shots to
vehicle occupants and vehicle damage.

Added tracer round script. When tracer rounds are fired a small
illuminating object is created and moved towards the target. More
visible from other player's perspectives and can be used to scare
targets or mark them for others.

Fixed an issue with /additem input inconsistency (IDs required space
delimiter, names required comma delimiter).