Validation mif

[leonieschweiger]

This PR introduces changes that are needed to read in data from existing sources used in mrindustry for the validation mif in mrmfa (see pik-piam/mrmfa#65).

1. A new figure from IEA The future of petrochemicals is read in via readIEA_Petrochem. Since it is only global data, no regional disaggregation is performed, i.e. the new subtype can only be called with convert=FALSE.
2. The convertStegmann2022 function is modified such that the data can now be either disaggregated based on FE weights (as before and still used in calcPlasticsEoL in mrremind), or based on population weights (as needed for the variables used in calcPlStegmann for the validation mif in mrmfa). The current implementation makes it necessary to adjust the function call in calcPlasticsEoL - I thought it would be good to make the weighting choice apparent. Another option would be to use FE weighting as a default.

[fbenke-pik]

Thanks, don't forget buildLibrary