By Catherine Hornby and Giselda Vagnoni ROME (Reuters) - Italy's economy minister has warned against scrapping an unpopular housing tax, stirring a new row in the shaky left-right coalition over the levy which Silvio Berlusconi's center right wants abolished. Scarcely a day passes without a new dispute in the government - an uneasy alliance of former adversaries forced to work together after an inconclusive general election - raising speculation it may fall in the autumn. ...