General powerup/buff system
With the advancements in inventory and resources, it's clear we need a better setup for the powerups and buffs.
This system would be separate from the items that provide the buffs (or powerups, whichever term we prefer), so mutators like instagib can simply replace the strength and shield items without completely overriding the handling of these buffs.
The buff effects should be able to apply to any entity without needing special code to be littered throughout the codebase. This will probably require more mutator hooks (assuming it's based in the mutator system).
Mutators like buffs and instagib should be able to provide their own effects with their items, via hooks into the buff system.
This would of course take the space of the powerups HUD panel, if a buff's timer is set to -1 (unlimited), no progress bar or time should be shown.