Produce QCSchema compatible output if input is QCSchema JSON

[awvwgk]

dftd4 should become aware of the possibility to work with QCSchema JSON. Either by detecting that the filetype a structure_type was created from is filetype%qcschema and automatically enabling the corresponding output or by creating a dedicated dftd4 qcschema subcommand which will work as a native QCEngine interface.

Necessary steps:

• detect filetype%qcschema (require mctc-lib>=0.2.4)
• check whether we are dealing with qcschema_input or just qcschema_molecule
• extract required info from qcschema_input (must compatible with dftd4.qcschema Python module)

Issues:

• requires direct dependency on json-fortran (should be optional)
• interacting with QCSchema JSON is general enough to warrant a dedicated library (mctc-lib or new project?)
• must be careful to not drop data from qcschema_input we don't care about