Add a recursive json finding function to CoolUtil.hx

[EgguMan]

I added a recursive function to CoolUtil.hx to allow the game to find Json's in folders, and sub-folders.

I can't quite implement it completely into the codebase, as I do not know anything about the newer mod classes, (I stick with 0.6.3) so if someone would like they could implement it to be used those.

Example use in code

// assets/characters/bf.json
// assets/characters/gf.json
// assets/characters/opponents/dad.json

characterList = CoolUtil.recursivelyReadFolders('assets/characters', true);

// ['bf', 'gf', 'opponents/dad']

[crowplexus]

very useful