Inventory from server

[satoshinm]

Depends on https://github.com/satoshinm/NetCraft/issues/18

[satoshinm]

Got a client-side inventory working in the web client https://github.com/satoshinm/NetCraft/pull/178, to make it server-side all the truth should come from the server:

• [ ] Send initial items to web client on load and add to hotbar (new command)
• [ ] Web client entity picks up items and updates web client
• [ ] Blocks mined break naturally and drop items which the client picks up on the server (not adding client-side)
• [ ] Server-side enforcement of block mining time
• [ ] Blocks placed take and subtract from server inventory, server-side enforcement
• [x] Game mode selection/prevention from server side (new command -- m,)