inventory frontend rewrite

[shocktail39]

currently, this is what the code for the inventory's frontend looks like:

this is basically unmaintainable. i'm trying to rewrite the inventory's frontend to be readable, and maybe i'll actually finish a project this time. this is not even close to feature complete yet, so hold off on merging.

[shocktail39]

putting some notes here for reference. there are four commands that the backend sends to the frontend:

• script-to-web-inventory
• script-to-web-settings
• script-to-web-receiving-item-queue
• script-to-web-nearby-users

and there are eight commands that the backend listens for:

• ready
• web-to-script-inventory
• web-to-script-settings
• use-item
• share-item
• web-to-script-nearby-users
• web-to-script-request-receiving-item-queue
• web-to-script-update-receiving-item-queue

currently, my rewrite sends ready and handles script-to-web-inventory. any other signals sent to it currently just get put in an alert.