fix(algebra/group_theory): split homomorphisms into additive and multiplicative homomorphisms
fix(algebra/group_theory): split homomorphisms into additive and multiplicative homomorphisms

soonhokong/lean,fpvandoorn/lean2,fpvandoorn/lean2,soonhokong/lean,fpvandoorn/lean2,fpvandoorn/lean2,soonhokong/lean,soonhokong/lean,soonhokong/lean,fpvandoorn/lean2