* reintroduce the swap_and_pop vs in_place_pop split for perf reasons
* rollback to a model with two iterators on virtual functions
* even faster range-erase/clear
* refine the try_erase to make it accept an iterator and a count (easier to work with at the call site)
* added a test for the stable clear
* added a note for future improvements
* added single type view overloads for ::storage to make it compatible with the multi-type view version
* removed the useless tuple from single type views
* updated operator|
* custom move ctor/op for the registry class
* no registry argument from storage emplace, remove, ...
* added sparse set context to forward variables to mixins
* removed sparse set user data
* added basic_sparse_set<E>::current to return known version of identifiers in set
* sparse arrays also contain updated entity versions, no more unused bits
* basic_sparse_set<E>::contains performs a strict version check
* sparse sets manage correctly foreign entities in all cases now
* no tombstone checks for multi-type views, zero-cost pointer stability model
* removed meta_type::is_integral (no alternative provided)
* removed meta_type::is_floating_point (no alternative provided)
* added meta_type::is_arithmetic, prepare for auto-generated implicit conversions
* removed meta_type::rank (no alternative provided)
* removed meta_type::extent (no alternative provided)
* removed meta_type::rmove_extent (no alternative provided)
* removed meta_type::remove_pointer ((*any).type())
* add owned_t utility
* change view def to basic_view<T, get_t<C...>, exclude_t<E...>>
* change group def to basic_group<T, owned_t<O...>, get_t<G...>, exclude_t<E...>>
* remove view dispatcher (reduce instantiations)
* make basic_view::traverse use the local policy
