New Saving format HDF5, based on version 1.8.12
Thanks to Goeffrey Mant for the nice job !

* Hdf5 third-party can be compiled now from scratch and installed as deps
* fixed with Geoff some bugs in CtSaving_HDF5

Made some progress, after discussion with Armando Sole and jerome Kieffer
improve the group/dataset organisation.

Modify CtSaving::_prepare to pass CtControl (needed for Hdf5)

Add Multiset saving mode

Close saving file at the end of acquisition or after a stopAcq

improved hdf5 format, acq/image/detinfo parameters now saved

added a calculate_chunk() function to optimized chunking vs image size

fixed scalar attribute and scalar datatset instead of array