🔄 Parsers: isolate parsing functionality as much as possible

[mbercx]

Currently the logic for parsing various EPW output files is defined as methods on the EpwParser. At least they are defined as a staticmethod, so a user that just wants to parse an output file doesn't have to use AiiDA. However, e.g. the parse_stdout method already has a logs input, which only makes sense in the context of "parsing through AiiDA".

I would like to separate the logic that does the actual parsing of the output files as much as possible from the AiiDA class. In my view, it should be in a separate package, similar to what I'm trying to achieve with aiida-quantumespresso and qe-tools. But for now, we could write all the parsers as functions in the (already existing) tools/parsers.py module, which are then used by the EpwParser class. In fact, I already see we have some duplication for the parsing of the .a2f file.

[ymzhang0]

Totally agree. I have some functions for parsing the anisotropic/isotropic gap functions, dos files, etc. I'll then make a PR for them.

[mbercx]

Great, thanks @ymzhang0! Then let's first add these functions in the tools/parsers.py module. Afterwards we can integrate them in the EpwParser.