Add seabirdscientific backend

[jessecusack]

Sea-Bird recently released a python package for reading and processing their instrument data:

https://github.com/Sea-BirdScientific/seabirdscientific

It seems like this could be used for reading hex files.

[gunnarvoet]

Thanks @jessecusack - I did not know about this! I had a quick look and their package still looks quite rudimentary but maybe good to use as backend in the future if they develop this further.

[TilmanJimenez]

The seabirdscientific package sadly currently only supports SBE 37 and SBE 19plus V2, which after a quick look at the instrument_data.py are not compatible with the SBE 9. For example the voltage words are 16bit (4 hex) long, while in the SBE 9 they are 3 (or 6 because they always have to be in pairs).