Use only terrain from server, remove local generation when online

[satoshinm]

Now that there are compact chunks, #136 - local generation / delta should be removed when /online.

For completeness, this should include server.py, which links the C world generator. Have it send and compress the full chunk data.

This should also fix unexpected local terrain generation as seen in WebSandboxMC, when only the centered chunk is expected:

as noted on https://forums.glowstone.net/post/246

WebSandboxMC is looking better and better all the time, but there was land outside of the limited web-based area, looked like the example terrain from https://satoshinm.github.io/NetCraft/