'base output class constructor
configuration kwords:
logger=<existing logging object> to pass in a logger
format=\'format string\' to override default formatstring for output class
pcap = filename to write pcap'

def __init__(self, *a, **kw):

    self.logger = kw.get('logger', logging)
    self.setformat(kw.get('format', self._DEFAULT_FORMAT))
    self.timeformat = kw.get('timeformat', self._DEFAULT_TIMEFORMAT)
    self.delim = kw.get('delim', self._DEFAULT_DELIM)
    self.nobuffer = kw.get('nobuffer', False)
    if ('pcap' in kw):
        self.pcapwriter = PCAPWriter(kw['pcap'])
    else:
        self.pcapwriter = None
    self.extra = kw.get('extra', False)
    if ('session' in kw):
        self.sessionwriter = SessionWriter(**kw)
    else:
        self.sessionwriter = None
