Before-the-Bell: Decode Genetics Falls  NEW YORK (Reuters) - Shares of Decode Genetics Inc.  &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=DCGN.O target=/stocks/quickinfo/fullquote"&gt;DCGN.O&lt;/A&gt; fell 19 percent before the market open on Friday, a  day after the company said PriceWaterhouseCoopers resigned as  its accounting firm.