Add support for MTA sentence

[a1rwulf]

We do work for the Yachting industry and deal with a lot of NMEA devices.
As part of our internal goal to centralize parsing, we decided to move all our parsing to pynmea2 and contribute back the sentences we come across in the field, starting with MTA.
I see that there were plans to phase this one out, but we still see it's being used by devices in the wild.

[hecko]

Out of curiosity which device is this specifically using this sentence? Thanks!

[a1rwulf]

@hecko I tried to figure this out, but I'm not exactly sure.
I believe it's a Moxa device, but can't give you a specific product as I don't have access to that information at the moment: https://www.moxa.com/en/solutions/marine

Edit:
It might very well be that the moxa units just multiplex the nmea inputs, so I really can't say which specific device we are talking about.

[a1rwulf]

Is there any procedure one is supposed to follow in order to get PR's moving?

[coveralls]

coverage: 97.977% (+0.005%) from 97.972%
when pulling 27b22c5 on yachtcloud:support-mta-sentence-upstream
into f298742 on Knio:master.

[a1rwulf]

Thanks!