Input parameter validation

[ezpzbz]

We need to add validation of input parameters. It can be implemented based on discussion in AiiDA Hackathon by defining a new Data class.
This will be done once the calculation and parser are well tested.
[UPDATE] Currently, I am working on having this validation on functional and basis set by:

• Having separate inputs for them instead passing them in parameters dictionary
• I need a list of supported functionals by ORCA as well as its Libxc interface.
• User provided functional would be checked against valid values and gets verified.
• In the case of basis sets, same story applies for the ORCA internal basis sets.
• In the case of basis sets, we can have a degree of automation to set proper flags if user requests RI, RICOSX, and RIJK approximations.

[danielhollas]

I am not sure if this is a good idea in general, it seems to me it would take a too much maintenance, and different ORCA versions may support different functionals and basis sets.

It would be great if ORCA provided a 'dry-run' option or some kind of input checker, but it doesn't seem to be the case.