move everything to subfolder theories/

theories/heap_lang/notation.v

theories/heap_lang/op_rules.v

theories/heap_lang/proofmode.v

theories/heap_lang/tactics.v

theories/heap_lang/wp_tactics.v

theories/prelude/base.v

theories/prelude/bset.v

theories/prelude/coPset.v

theories/prelude/collections.v

theories/prelude/countable.v

theories/prelude/decidable.v

theories/prelude/fin_collections.v

theories/prelude/fin_map_dom.v

theories/prelude/fin_maps.v

theories/prelude/finite.v

theories/prelude/functions.v

theories/prelude/gmap.v

theories/prelude/gmultiset.v

theories/prelude/hashset.v

theories/prelude/hlist.v