New CVars: mp_weapondrop and mp_ammodrop and fixes

[dystopm]

• Added cvar mp_weapondrop which controls behaviour on weapon drop after death. You can choose between (0) do not drop anything after death, (1) drop your heaviest weapon (default behaviour), (2) drop your active weapon or (3) drop all your weapons. It works independently of mp_nadedrops cvar (and it's also an extension of it)
• Added cvar mp_ammodrop which controls behaviour of ammo packing on weapon boxes drop. You can choose between (0) keep ammo on player always, (1) drop ammo on weaponbox only after death and (2) drop ammo on every weaponbox you drop either death or manual drop.
• Fix: Ammo resetting inside CreateWeaponBox; ammo was not getting reset if packAmmo = true, no matter if weapon is not considered "exhaustible"
• Fix: CanDrop used inside PackDeadPlayerItems in case modders want to make a weapon undroppable.
• Code related: PackPlayerItem now returns the entity created.
• Changed usage of constants meaning (GR_PLR_DROP_GUN_* inside DeadPlayerWeapons) and added an extra.

Related to/fixes close #520 #620 #758 #821
Tested, work as intended

PS: Cvar's names/description corrections are welcome

[StevenKal]

Nice!
But maybe dropping "all weapons" when "GR_PLR_DROP_GUN_ALL" is set could be added (all primary & secondary).
And keep "GR_PLR_DROP_GUN_ACTIVE" for only active weapon on death (if, it is a primary or secondary, however, get & drop best weapon). But a new rule like "GR_PLR_DROP_GUN_BEST" could also be welcomed.
Or, make "GR_PLR_DROP_GUN_ACTIVE" drops best primary/secondary weapon (default behavior), but this does not really match to the rule name...
So, questionable.

[SergeyShorokhov]

Code style fixes

[dystopm]

Nice! But maybe dropping "all weapons" when "GR_PLR_DROP_GUN_ALL" is set could be added (all primary & secondary). And keep "GR_PLR_DROP_GUN_ACTIVE" for only active weapon on death (if, it is a primary or secondary, however, get & drop best weapon). But a new rule like "GR_PLR_DROP_GUN_BEST" could also be welcomed. Or, make "GR_PLR_DROP_GUN_ACTIVE" drops best primary/secondary weapon (default behavior), but this does not really match to the rule name... So, questionable.

I've been thinking on a nice way to implement that. Thing is: drop weapons separately guided by player angles (left to right, depending on how many weapons player will drop) or drop weapons in forward, each one further forward than the last (easy implementation, just store them into an array and apply an scalar to their current velocity since all are going forward) - will take a look and then test

[dystopm]

Added new behaviour: mp_weapondrop 3 (as @StevenKal requested) will ensure players drop all their weapons (primary and secondary) after death. It basically uses the same pattern but every box created has more velocity than its predecessor. Depending on physics, players can stand still, be on mid air or just running fast, and that will affect weapons drop spreading.

Used sv_cheats 1 and impulse 255 for testing purposes only, because in legit scenarios players can have at least 2 weapons.

Credits to @metita for his help in test scenarios.

[SergeyShorokhov]

The CBasePlayer::PackDeadPlayerItems() function looks terrible (it's not because of your PR). It needs refactoring (later), for the logic is hard to track. 😞

[dystopm]

@wopox1337 yeah you're right, I just tried to stick to the original code but indeed it is certainly bad coded