move precategories to separate folder and rename to wild categories (#…

…1103)

* introduce wild categories, copying from precategories

refactor (split into files)
rename
add instance for Types

* split further

* define univalence, fix things

* add path category

* refactor use case

* remove now obsolete precategory

* update refs in Papers

* move instance (of WildCat)

* rename

* remove duplication