PTNL PJK File Update

[arcsump]

Hi @Knio ,
Thanks for the awesome library,

I needed to extend a proprietary class, wondering if it can be properly incorporated.
That would be great, many thanks again - I am not that well-versed so yeah pardon me.

Meanwhile, I modified tnl.py and added this snippet

class TNLPJK (TNL, DatetimeFix):
fields = (
('Empty', '_'),
('Sentence Type', 'type'),
('Timestamp', 'timestamp', timestamp),
("Datestamp", "datestamp", datestamp),
('Northing', 'northing'),
('Northing Direction', 'northing_dir'),
('Easting', 'easting'),
('Easting Direction', 'easting_dir'),
('GPS Quality', 'gps_quality'),
('Total number of satelites in use', 'num_sats'),
('DOP', 'dop'),
('Height of Antenna Phase Center, GHT or EHT', 'phase_center_height'),
)