Maintaining website (#459)

* Try to build website during development

* Corrected path to coverage-badge

* Updated paths to files to get rid of warning about inclusion of python-files from project

* Try to use "absolute" paths for images (relative to top source dir)

* Another path (unclear why different from other rst-feils)

* Updated docstring to be included verbatim in website

* Updated names of links to avoid duplication

* Another try with updated paths to images

* Corrected formatting of file (so satisfy black)

* Smaller matrix for faster CI during development

* Went to "normal" path for images

* Raise an error if image were not found to prevent a falsy website from being published

And added find command to get location of images

* Added plotting of MPI-images

* Let the whole CI run

* Run tests for more python-versions and increase timeout to MPI-Jobs

* Added print to debug MPI issue and reduced parameters for debugging

* Removed unused import and corrected linting

* Removed unused code

* Exit after all images are created (not only first one)

Print info after creation and check of image

* Changed creation of figures and added continue at the end of each iteration

* Moved plotting into own function

* Reduced projects to be tested for fewer CI-jobs

* Plot only singe param

* plot multiple setups

* Create image differently

* Replaced plotting function

* Remove variables at end of loop

* Skip entries from setup_list

* Approach with fully enclosed plotting-function and newly loaded results each time (to avoid modifications in one run affect following ones)

* Corrected typo and formatting

* Use functions of objects instead of plt or helper-functions

* Updated setters for axes-object

* Create all four plots

* Return a whole slice of list (shallow copy)

* Moved loading of results into plotting func

* Cant delete variable if created in other scope

* Duplicate list where looped over

* Use explicit repetition instead of loop

* Plot all 4 plots

* Run MPI and plotting in two separate processes

* Reformatted using black

* Run plotting in main process

* Run plotting in subprocess, passing cwd and env

* Replaced subprocess.popen with run

* Moved import of results only once

* Show created png-files

* Use plt-helper again (as it was initially)

* Run two different numbers of num_procs for MPI

* Run all tests again

* Don't print png-files, as this does not exist everywhere

* Corrected issues in parsing output of sphinx

* Run postprocessing only in main repo

And removed unused code (comments)

* Include changes from master, that were merged upstream recently (Handling SLURM issues and combining workflows)

* Changed the text of links in documentation to be less ambiguous

* Changed way to mark code-blocks

thank you @tlunet for the pointer

* Corrected formatting

* Fetch artifacts only after running Gitlab-CI (otherwise merging is not needed at all)