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**
OK I delete the `end` messages. Every begin of a section is also a end of the previous section.
During a normal load you only see this messages if you enable the debug output.