Prepare a Picard commandline.

def cl_picard(self, command, options, memscale=None):
        """Prepare a Picard commandline.
        """
        options = ["%s=%s" % (x, y) for x, y in options]
        options.append("VALIDATION_STRINGENCY=SILENT")
        return self._get_picard_cmd(command, memscale=memscale) + options