Refactor yaml

[coco875]

it split asset in four folder (categories), models, textures, others, sound.

• add docs about organisation of assets
• see with modders
• fix textures issue because path are too long

[coco875]

thing to do:

• finish to fix kart animation (tumble are not correct and wheel can't spin yet with custom texture)
• finish to make yaml for other course who unpack dl
• create the factory for course vtx who tranform it to vtx
• add link between them gfx and vtx of course to allow to use them
• in extra mode see if just use a matrix of transformation to invert y and invert the sense of culling are enough

[coco875]

make a break on this pr because it's annoying and want to do something else then spaghettikart.