Add mandatory HDF5 support to WHIZARD.

[Juergen Reuter]

One of the ideas of the parallelization workshop was to put more emphasis on the HDF5 format, as it allows for more efficient I / O, compression and parallel I / O. Especially with regard to future computational requirements, such as 8- or 10-particle states, special emphasis must be placed on the reading and writing of the grid files, since their size increases linearly with the number of channels, and can reach several Giga-bytes, which are read and rewritten for each iteration. This adds a (non-parallelizable) runtime to WHIZARD. Furthermore, it can be applied to the internal event format.

[Juergen Reuter]

Back as Gitlab issue 251.