Refactor egfrd::World

[kaizu]

[kaizu]

• World -> ParticleContainerBase<World<Ttraits_>, Ttraits_> -> ParticleContainer<Ttraits_> -> ecell4::Space.
• Transaction -> ParticleContainer<Ttraits_>, and TransactionImpl<Tpc_> -> Transaction<Tpc_::traits_type>.
• MultiParticleContainer -> ParticleContainer<traits_type>.
• ParticleContainerBase stores MatrixSpace<particle_type, particle_id_type, ecell4::utils::get_mapper_mf> as its member variable.
• Multi stores MultiParticleContainer.

[kaizu]

The benchmark shows ParticleSpace properly replaces MatrixSpace. See also https://github.com/ecell/ecell4/blob/4-1-stable/misc/benchmark.png