Feat items

[apachano]

Authors: @apachano

Summary of changes

• Implements base framework for item implementation
• Implements item registration through Lua
• Switches player hand from blocks to items
• Implements stored value for blocks dropping items

Caveats

• Item and block places/drops store strings as arguments to allow for registration without the target existing
• Block drops functionality is not actually implemented

QA Notes

• Functionally nothing should be different than before
• Only registered items are available for the hand selector, blocks should not be

On approval

Merge

[tobyplowy]

LGTM. Builds, runs, items work. Good job!