Add beta-cyfluthrin as target for cyfluthrin

[fchichorro]

Ecoinvent maps recipe cyfluthrin to beta-cyfluthrin. We could do the same, i.e., to use cyfluthrin as a proxy for beta-cyfluthrin? The advantage to that is that ecoinvent processes with beta-cyfluthrin get impacts for this elementary flow. I used the recipe cyfluthrin to fedefl cyfluthrin as a template to create the new flow mappings. @ErCollao @ganorris.

[bl-young]

Hi @fchichorro thanks for digging into all of these. One minor request: we try to maintain the flowables and contexts separately, so in most of the cases you've submitted, you can simply add one line to the flowables mapping file (e.g. ReCiPe2016FlowableMappings.csv), and then run the script build_lcia_mapping.py (note you'll need to change the target LCIA method in line 14).
This should update the mapping files exactly as you have already done, but it reduces the risk of typos and such.

This may not work for #164, which will require a different approach.

[fchichorro]

Hi @bl-young, thank you for the feedback. I had indeed not noticed those functions, I will surely use them for any subsequent commit.