* Three-member panel to investigate crimes by all sides * Due to report by March 2015 to UN Human Rights Council By Stephanie Nebehay GENEVA, Aug 11 (Reuters) - The United Nations on Monday named three experts to an international commission of inquiry into possible human rights violations and war crimes committed by both sides during Israel's military offensive in the Gaza Strip. William Schabas, a Canadian professor of international law, will head the panel whose other members are Doudou Diene, a veteran U.N. human rights expert from Senegal, and Amal Alamuddin, a British-Lebanese lawyer engaged to be married to Hollywood actor George Clooney.