Wall St Seen Edging Up on Crude Price  LONDON (Reuters) - Wall Street was expected edge higher at  Tuesday's opening as the price of U.S. crude oil eased, with  insurers firming after the head of Marsh   McLennan Cos.  Inc.&lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=MMC.N target=/stocks/quickinfo/fullquote"&gt;MMC.N&lt;/A&gt; resigned.