Remove Yaml Dependency

[nsmryan]

We only use one yaml file, and it doesn't really have to be a separate format. This will not remove the serde dependency, as this is used to save and load the game, but it should remove at least a few like 'serde-yaml", 'ryu' and 'rust-yaml'.

Probably split the color palette into a separate file, and then parse a config.txt file manually. This will likely require some code for each entry, but it should be easy to extend.

The disadvantage here is that we would no longer be able to load as many Rust structures, like enums or structs. However, we only do this for the map config, and we can probably live without it.