In order to reduce some CPU & disk load when trying to generate dungeons.

Everytime a dungeon tries to generate, RLD parses all the settings files in case they were modified on the fly.
But since this is a very unfrequent scenario, I suggest this:

1. Parse all json settings files when loading a world, and when running /roguelike settings (list/reload).
2. Save the parsed data and each file's Modification date and time, inside this cache object.
3. When trying to generate a dungeon, check:
   • if current settings json file's modified date and time equals the cache timestamp, skip this parsing.
   • else, parse this json file and update its corresponding portion of the cache object.
   • continue with generation.

The goal is to take all dungeon generation settings from RAM instead of the disk. I hope it makes sense.

This was fixed in 5a7988a I think