EXAMPLES
* filter on runtime values/variables (not only types)
* support to polymorphic types (see #859)

DOC:
* custom storage/view
* update entity doc when the storage based model is in place
* in-place O(1) release/destroy for non-orphaned entities, out-of-sync model
* view: single vs multi type views are no longer a thing actually
* bump entities, reserved bits on identifiers

TODO:
* resource cache: avoid using shared ptr with loader and the others
* further optimize exclusion lists in multi type views (no existence check)
* further improve meta resolve function by id (bimap)
* get rid of observers, storage based views made them pointless - document alternatives
* deprecate non-owning groups in favor of owning views and view packs, introduce lazy owning views
* bring nested groups back in place (see bd34e7f)
* work stealing job system (see #100) + mt scheduler based on const awareness for types
* view: improve construction of base, reduce inst due to/improve perf with index-based approach in dispatch_get/pick_and_each/each (single type too)
* view: update natvis as needed after the last rework, merge pools/filter in the same array, drop check (?) and turn view into a position
* view: Type-only view_iterator (dyn get/excl sizes)
* view: Type-only basic_common_view (dyn get/excl sizes with pointer to array from derived)
* combine version-mask-vs-version-bits tricks with reserved bits to allow things like enabling/disabling