Move some of the structure plotting functions from contrib

[pmrv]

They were previously defined on the TrainingContainer over in contrib, but I have added also distances to plot a plain histogram of nearest neighbor distances.

Corresponding PR to contrib once this is through.

[Leimeroth]

So TrainingContainers plotting interface should inherit from this than?

[pmrv]

Yeah, that's how I was planning it. These plotting functions would be purely concerned with structural data and the training container ones would then only add things related to energies, forces, etc.

[Leimeroth]

I like the idea. If some errors occur down the line we should fix them there.

[pmrv]

I didn't want to pull in seaborn for just one plot, so I put it in an ImportAlarm. @niklassiemer are we tracking our opt deps somewhere?

[pmrv]

I also remembered to update the change log. :')

[coveralls]

Pull Request Test Coverage Report for Build 2829084886

• 20 of 127 (15.75%) changed or added relevant lines in 2 files are covered.
• 202 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.4%) to 68.223%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyiron_atomistics/atomistics/job/structurecontainer.py	1	6	16.67%
pyiron_atomistics/atomistics/structure/structurestorage.py	19	121	15.7%

Files with Coverage Reduction	New Missed Lines	%
pyiron_atomistics/atomistics/job/structurecontainer.py	1	74.71%
pyiron_atomistics/vasp/base.py	201	65.51%

Totals
Change from base Build 2819709769:	-0.4%
Covered Lines:	11866
Relevant Lines:	17393

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💛 - Coveralls

[jan-janssen]

Looks good to me