map data sharing server

[Gjum]

• there needs to be some encryption as well as authentication against mojang so we can do access control later on
• when the server receives a chunk map data packet, it sends it to all clients who don't have it yet (by tracking which clients have observed which chunk map data hashes), and writes it to a database (schema here)
• eventually clients will also receive data mapped by others during the client's absence when it connects again moved to #5