Deprecating Full XML input in LCAO (molecule and solid)

Due to the complexity of maintaining full XML files (where basissets, MO_coeffs and multideterminants explicitly written) and HDF5 format where everything is hidden, I would like to see if it is possible to deprecate a fully XML input file.

We would like to remove some duplicated tags that could lead to inconsistencies if touched, handle the IO when optimizing orbitals or CI-Coeffs but maintaining both (XML and HDF5) will duplicate code and at this point we already saw confusion reading the code as we have to look for function names with _h5 or _xml. In many cases the behavior of the code is unknown for a few cases without HDF5 support.. Also, at this point, we are forced to follow the position of the line in the XML, so the builder follows a strict sequence. If we want to move things around it becomes very difficult.

Primary gap will be with CSFs (do not know anyone using that path), but it is easy to rebuild if needed.
If agreed, we can list the gaps and see how hard/time consuming it will be to cover them.

Anouar and Ye