Ability to handle custom save file layouts

[Pulverizer]

Similar to YAML flow style but allowing the user to override on a per-node basis. eg. YAML Block Style:

flyblocks:
    minecraft:wool:
    - 50.0
    - 100.0
    ?   - minecraft:chest
        - minecraft:trapped_chest
    :   - 0.0
        - N50

vs the plugin I'm porting:

flyblocks:
    "minecraft:wool": #wool represents lift
        - 50.0
        - 100.0
    ["minecraft:chest","minecraft:trapped_chest"]: # limit chests to make big airships important for merchant missions
        - 0.0
        - N50

[zml2008]

Looking into SnakeYAML, this should actually be possible -- we'll want to migrate from using their load/dump API to using their compose/represent APIs to give us more control.

This will require RepresentationHints to be added to nodes, so it won't make it in for 3.7