‘year’ set on scenario != ‘year’ set in GAMS

[gidden]

Perhaps this is impossible to fix at the moment, but I ran into many many headaches before realizing that there is not a one-to-one mapping between s.set('year') and the set year in a GAMS gdx file. Moreover, the set year in a MESSAGE GDX file is not consistent with the set year in a MACRO GDX file. It would be nice to harmonize these..