Close #419 Radiation Adds HDF5 Output/Restart

This pull request:
- adds hdf5 via libspash to radiation plugin
- removes amplitude data as pure binary 
- instead adds amplitude data as HDF5
- adds correct checkpoints via HDF5
- adds automated restart
- improves seperation between communication and data write

It solves #419.

In upcomming pull requests:
- conversion factors to SI
- observer directions
- frequencies

will be stored in the HDF5 files as well
and tools for data analysis will be created. 
you could also use hdf5 at this point, why do you prefer ascii? :)