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**
(regarding some comments in the kernel code:) at least add a comment what is in every slot of this buffer, better use a `#define`