LinkEvent added, RenameEvent fixed, logger optional

RenameEvent: 'Channel' renamed to 'Oldname'. http://www.voip-info.org/wiki/view/asterisk+manager+events#RenameEvent

LinkEvent added. http://www.voip-info.org/wiki/view/asterisk+manager+events#LinkEvent

ClientImpl: _logger not used if log4php.properties not in constructor options