improve n[] notation for nonexpansive maps: the proof of Proper is no longer required, it can be derived from nonexpansiveness

write an interface to world_prop, and make iris_core (assertion logic + world satisfaction) work with it

definitions pushed through, some lemmas commented out for now.

carrier of the monoid. This now corresponds exactly to the formulation
of monoids in rose.v

laters are now proved (*not* the lemmas about later commuting with stuff).