entt/TODO

* long term feature: templated generic vm
* long term feature: shared_ptr less locator
* long term feature: shared_ptr less resource cache
* custom allocators and EnTT allocator-aware in general (long term feature, I don't actually need it at the moment) - see #22
* debugging tools (#60): the issue online already contains interesting tips on this, look at it
* define basic reactive systems (track entities to which component is attached, track entities from which component is removed, and so on)
* define systems as composable mixins (initializazion, reactive, update, whatever) with flexible auto-detected arguments (registry, views, etc)
* runner proposal: https://en.wikipedia.org/wiki/Fork%E2%80%93join_model https://slide-rs.github.io/specs/03_dispatcher.html
* work stealing job system (see #100)
* meta: sort of meta view based on meta stuff to iterate entities, void * and meta info objects
* meta: move-to-head optimization when searching by name on parts (data, func, etc)
* hashed string: add implicit check on construction for uniqueness (optional)
* destroy overload that accepts a couple of iterators (see create)
* allow for built-in parallel each if possible
* travis + windows is now available, try it
* events on replace, so that one can track updated components? indagate impact
* tags revenge: if it's possible, reintroduce them but without a link to entities (see #169 for more details)
* empty components model allows for shared components and prefabs unity-like
* provide create with a pack of default constructible components to assign
* allow to replace std:: with custom implementations
* allow to sort groups (::respect can already work with begin/end instead of a whole sparse set)
* README file: add section with contacts (gitter and the others)
* cleanup - see https://github.com/skypjack/entt/commit/ad5cedc08c83e8cbcc8aaeac9634d44624ffe35a#commitcomment-32380903

==> can we do more for shared libraries? who knows... see #144
* get rid of get_pool_data (welcome structured bindings)
* to be updated: dispatcher
* to be updated: registry
* to be updated: emitter
* to be updated: doc