[Bug Report] Thread and Process safety - Chunk caching

[gentlegiantJGC]

Bug Report

The chunk caching system is not process safe and needs improvements to handle multiple processes.

Current Behaviour:

Currently we have a single cache database for data which would be shared if multiple processes were spawned. Since the leveldb database we are using is not thread safe it will cause issues if it is opened from multiple places.

Expected behavior:

We should be able to spawn multiple processes and have them all work independently without any issues.

[gentlegiantJGC]

I am going to migrate https://github.com/Amulet-Team/Amulet-Core/issues/154 to here because the core bug tracker is not viewed much.