add some standard regionmapping files for ISO to R5 and R10, and from REMIND to R10
refactor convertHistoricalData such that the CountryCode;RegionCode combination is accepted as well as REMIND;project_region, and that if you just pass "REMIND_2_R10" as regionmapping, it picks it from the inst/regionmapping folder
Purpose of this PR
CountryCode;RegionCodecombination is accepted as well asREMIND;project_region, and that if you just pass "REMIND_2_R10" asregionmapping, it picks it from theinst/regionmappingfolder