Multi Species Particle Load from hdf5

- rewrite how partilces are loaded from HDF5 file
- add support for arbitrary species count
- particles load now done on gpu
- remove old method
- SimulationHelper: show init time in output

~~**Please do not merge before #514**~~
same from my side, I see no use in writing that obfuscated lines. If the compiler optimizes `signed` better than `unsigned` vars than it is simply because it is dump and far from the real world.
I would also favor readable code with less type conversions over micro-optimizations like that.