Add support for multiple inventories

Add the ability to keep track of different inventories and move items between them. Allow inventories to ignore the weight in them.

Separate settings for each inventory, settings button inside of the inventory model?

• Update models
• Update backend models & services
  • Item service
  • Inventory models
• Websocket methods
• Make inventory navigation bar dynamic
• New inventory button
• Remove inventory button
• Modal form for new inventory
• Per-Inventory settings