Make Configs editable from in-game

[cubefury]

Supersedes #43

Changes:

1. Convert configs to GTNHLib system
2. Make settings editable from ingame
3. Write back settings to config when a player changes the display type and sort mode from within the vending machine gui

Tested on daily 214 in both SP and MP:

1. Validation of display type and sort mode when it is changed
2. Change configs from Mod Options in main menu
3. Change configs from Mod Options while in-game
4. Changing display type and sort mode from within vending machine gui

Breaking Changes

1. This change will override any existing vendingmachine.cfg file and reset the config settings for existing instances when the mod is loaded. Trade database and character trade states/coin data are not affected.

Dev notes:

1. DisplayType and SortMode classes should really be refactored out into their own files, but I will do that in a separate PR.
2. I dont really know what to do with that lone unsaved world_dir config that's only populated at runtime, there's no other real "session" class where it would logically belong, so I just left it in there

[Caedis]

The config guis are automatically generated if you do not provide one btw

[Caedis]

https://github.com/GTNewHorizons/GTNHLib/blob/master/src/main/java/com/gtnewhorizon/gtnhlib/mixins/early/fml/MixinGuiModList.java#L39

[cubefury]

yee i just listed that breaking change cuz it'll override any existing config file with the new format, in case someone loads this up and wonders why their settings got reset