[WIP] ABINIT DFPT SHG

[VicTrqt]

Summary

• Different Makers needed for DFPT (DDK, DDE, DTE, Mrgddb)
• A full DFPT SHG workflow to get the SHG and the dielectric tensor

TODO

• Write some tests
• Figure out a way to use the power-ups despite the Response(replace=) for the DDK and DDE
• Is a restart of mrgddb necessary ?

[gpetretto]

Thanks for porting the DFT workflows to atomate. I went thorugh the code and left some comments.

I would say that the main one concerns anaddb. I don't think that

1. anaddb should be run inside the mrgddb job. It should have its own Job and input generator, since it is much more likely to be customized compared to mrgddb.
2. the outputs of the postprocessing with anaddb should be in the mrgddb output document.

An additional point that is not present in the comment concerns the fact that, if I am not wrong, with the introduction of the DFPT workflow the abipy manager should be configured, while before it was not needed. It probably being used to generate the list of pertrubations and to run anaddb behind the curtains. I am wondering if there should be some specific configuration in atomate dedicated to that. Maybe it will be worth to discuss this point more in detail.