ADEN, Yemen (Reuters) - Yemeni warplanes and troops bombarded the Islamist militant stronghold of Jaar on Monday, officials and witnesses said, part of a U.S.-backed offensive in a country Washington sees as a front line in its war against al Qaeda. At least 44 soldiers and militants were killed as the army launched its most serious assault on Jaar to date and also attacked positions near Shaqra, a coastal town on a major shipping route, and other areas, a Yemeni military official told Reuters. ...