UM-010: Bucket Hat + Bucket Suicide

[UrsulaMejor]

• Added logic to Chemistry-Tools.dm for turning regular bucket upside down to make bucket hat
• Added bucket hats to clothing/helmets.dm
• Added blocks_vision var to hats in clothing/hats.dm
• Added logic to human.dm to check hats for blocks_vision
• Added new icons to head.dmi and item_hats.dmi for new bucket hat item state + worn states
• Added "[user] kicks the bucket!" suicide to buckets, bucket hats, and bucket helmets (feel free to get rid of this part, I just thought it was cute)

Bucket hats block vision and look really silly. Bucket suicide kills you instantly with a funny message. Neat.