…cci/aiidalab-qe-vibroscopy into lazy_loading_compatible

missing: download of the data, proper testing,
detached app.

The problem was that the default value of a tl.List(tl.Float())
is tl.Undefined. Now we explicitely reset the default value
of Q0_vec, h_vec and k_vec

For now, I added it at the end of the main EuphonicBaseResultsWidget.
It will only allow to download phonopy.yaml and fc.hdf5. The plots can be downloaded in the corresponding tabs.

I added a method to the model which produce the downloadable files, and left the actual
_download_data method in the widget. I think this is a proper design as the model manipulates data,
the view can provide them.

Still missing the download of single tabs, for now it does not work