Add a parameter for csv output date format

Add a command line parameter to customize the csv date format appended before each result line.<p>Migrated from http://code.google.com/p/jmxbox/issues/detail?id=2</p><hr/><h2>earlier comments</h2>

<p><strong>jarcand@appbox.ca said, at 2013-04-16T02:21:15.000Z:</strong></p>

<p>Migrated to http://github.com/jeanarcand/jmxbox/issues/2</p>
