Change example filename extension

[kdund]

We found that some people did not realise that inference_interface was the way to look at files, templates etc.
In an effort to make it clearer, I thought we might change filenames to .ii.h5 (not mandatory, of course, filenames can be anything)
Also I added an exclude so the flake8 will not enforce line length in .rst files for example :)

[github-actions]

Pull Request Test Coverage Report for Build 6338939120

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 91.741%

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Totals
Change from base Build 6284754830:	0.0%
Covered Lines:	1333
Relevant Lines:	1453

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💛 - Coveralls

[hammannr]

Looks good @kdund ! And the paragraph in the documentation is very helpful I think 😊 .
I found two more occurrences of .h5 in the 3_sensitivity.ipynb notebook and the defaults of the Runner class. It probably makes sense to also replace those.

[hammannr]

prfect, thanks! 😊 I'll merge this now so that we can merge #127 afterward