Rework drop and pickup items feature

Refactored the drop/pickup items feature into functions, and added
conditions to prevent glitch where player is able to pickup item
multiple times by spamming the pickup action. Pickup action is now
removed automatically by the game engine when activated.
Modify gang player uid to use same id that is used by stats

The previous gang uid used to contain parts of the player's name. This
was meant mostly for testing, to be able to spawn multiple clients,
with same UID, and join gang.