By Stephanie Nebehay MEZIERES, Switzerland (Reuters) – Usher, Lauryn Hill, Macy Gray and Erykah Badu are booked to perform at the Montreux Jazz Festival during its 51st edition, organizers said on Thursday. The eclectic lineup for the June 30-July 15 event includes Ibrahim Maalouf, Beth Ditto of indie rock band Gossip, Phoenix, as well the…