Thull dive number depth

[tomhull]

The current calc_dive_phase and related functions are not suitable for shelf sea work as they assume valid dives are deeper than 200 m.
This pull request adds new threshold variable to the minimum valid dive depth can be adjusted. The default has been changed to 15 m which feels deep enough to avoid heavy swell.
Additionally, I’ve included a test for calc_dive_number.

[jbusecke]

Thanks a lot for the great contribution @tomhull.

I had some minor comments about the defaults and a suggestion for extending the test. Should be ready to merge very soon.

[jbusecke]

Sorry for the delay @tomhull, I was on vacation. Lets check back on this when the test have run.

[soerenthomsen]

@tomhull and @jbusecke this looks like it is almost done or?

[jbusecke]

Definitely needs to be rebased and we should wait for a fix to #149

[MartinMohrmann]

@tomhull Thanks for the contribution and for including a test! :)
Please remove the unnecessary import of pytest from the file test_dive_numbers.py though. See the failed code-style test result.

Why are you dismissing this review? The discussion about the minimum valid dive depth has been here for over two years now. I believe this should no longer be a reason to block the nice contribution of @tomhull to be finally merged.

[MartinMohrmann]

The provided change to make the dive_depth_threshold adjustable is essential for shelf/coastal seas. Tests are provided and working.