Added GivePlayerStuff functions.

The item system is pretty complicated so I've added straightforward functions to give player some health, armor or ammo: GivePlayerHealth, GivePlayerArmor, GivePlayerAmmo and GivePlayerFuel.

Also, I've started refactoring the code to make a unified resource system where each resource is treated with the same code. Currently, I've added GivePlayerResource that will handle giving resources to players. GivePlayerHealth, GivePlayerArmor and GivePlayerFuel call GivePlayerResource. It will be refactored later to add stuff such as mutator hooks and ammo regeneration in the next MR.