Create series implications for Agarest Senki.
agarest_senki -> agarest_senki_(series)
agarest_senki_2 -> agarest_senki_(series)
agarest_senki_mariage -> agarest_senki_(series)
agarest_senki_zero -> agarest_senki_(series)
Not sure if we need an agarest_senki -> agarest_senki_1 alias as well.