Numos.Chunks package

[Roudenn]

About PR

Adds a Numos.Chunks project & package that contains stuff related to voxel chunks in Numos's implementation.

Only does abstraction, renaming and reorganization of code, PR doesn't change anything about how the chunk system works, except for removing some redundancies such as passing the dimensions when they're already defined.

Why

Required for #35 because pipes should be stored in a separate voxel grid that is also able to be compatible with the atmos simulation.

This PR only implements parity for the chunk code layer (voxel operations such as finding neighbours & supporting docks and portals are still hardcoded to atmos), but still does progress towards supporting custom modules better.

Making voxel operations abstract will require a lot of work and multiple thermonuclear refactors, so this PR is okay to be merged as a "Part 1" before going deeper into abstractions.

Changes

• AtmosChunkConstants now only has atmos-specific chunk stuff (InitialGasChannelCapacity), the rest is split into ChunkConstants class
• AtmosChunkHandle renamed into ChunkHandle and moved from the API to Numos.Chunks
• Added abstract Chunk class that contains stuff that should be shared for all voxel chunks with some helper methods, it's inherited by AtmosChunk
• Chunk map dictionary is now managed by the ChunkMap<T> (where T is a Chunk type) class, AtmosKernel stores an instance of that class to do chunk operations

[Roudenn]

Will be ready for review when I fix the tests