Move data out of scene.json to improve performance/compression

[jackjt8]

Scene
\ scene_summary
\ scene_settings
\ scene_entities
\ scene_chunks

Scene - Compressed file/folder containing all individual scene components. Each component can be made to be as efficient as possible to store said data. Keeps portability high as people can simply share a "file" like they did previously with scene .json.

scene_summary - Improve performance of Load Scene dialog by not parsing data we don't need. Contains: Name, Number of Chunks, Size (canvas resolution), Current SPP (maybe do current/target?), Render Time, Last Modified

scene_settings - Bulk of scene data. Water settings, fog, materials, cameras, etc.

scene_entities - re:#930 - A huge portion of the scene file ends up being entities...

scene_chunks - Similar issue to entities. Large selections can lead to a really long Chunk list.

---

If possible keeping the extensions of these files as .json would be best as they are easy for humans to read and edit. We could use gzip, lzma, or other forms of compression on certain components.