Decode status variables

[jmcvey3]

1. temp_mag variable is an uncalibrated thermistor, per Nortek integration guide, so it's been dropped
2. Decoded status, status0, and alt_status and saved as variables or attributes
3. xmit_energy isn't necessarily constant and has been added back as a data variable rather than an attribute
4. rename quaternion to quaternions

Setting as pull request to triple check everything before merging into main

[coveralls]

Pull Request Test Coverage Report for Build 2029590731

• 63 of 65 (96.92%) changed or added relevant lines in 8 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.06%) to 90.682%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dolfyn/io/nortek2_lib.py	28	30	93.33%
<!--	Total:	63	65	96.92%	-->

Totals
Change from base Build 2017114758:	0.06%
Covered Lines:	4613
Relevant Lines:	5087

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💛 - Coveralls

[lkilcher]

This looks good to me.

[jmcvey3]

Changed some status attributes to variables because it appears they can change with time. Removed 'status0' and 'alt_status', but left in the 'status' variable because it's an easy way to check if a ping is missing as it will never otherwise = 0.