Components and systems just can't be initialized at startup, so we need
some kind of explicit initialisation. I followed the same layout as the
others modules by adding a core class (Ndk::Sdk) which will initialize
components and systems, and Nazara's modules.
This is starting to get serious, I like it.
Former-commit-id: 263500e8d16db70ef7f92047b8a7e3235c08bcd0
EntityHandle are no longer required to pass Entity as arguments
World::CreateEntity() now returns a const EntityHandle&
Former-commit-id: 6fc53ce5759a2a508094bdc61b4471f13f0844ec