Fourth-order correction for cumulants

Adds the fourth-order diffusion correction to the D3Q27 cumulants, as proposed in Geier et al. (2017). Also adds the possibility to use limiters for the third-order cumulants in order to increase stability.

This MR depends on the MR pystencils!338 (merged) and can only be merged afterwards.

requested review from @holzer

assigned to @schottenhamml

changed the description

added 9 commits

• 5a718033...37fb1ede - 4 commits from branch master
• e6b5cea8 - Extend JSON serializer for other parameters.
• ec174eec - Add test for lbmpy JSON serializer.
• de143f82 - Use sympy numbers to ensure type safety.
• 0c2b2015 - Merge remote-tracking branch 'origin/master' into mr_fourth_order_cumulants
• 5da49533 - Replace forgotten ints by sympy floats.

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added 1 commit

• 552ec52e - Fixes for flake8 check.

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marked this merge request as ready

added 1 commit

• c19bf20b - Fix small shear wave scenario and mark full parameter study as long run.

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added 1 commit

• a132d378 - Fix reference.

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• 91a2d0fc - Exclude new tests when blitzdb not found.

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• 00f27770 - Also exclude database file if blitzdb not found.

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approved this merge request

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merged

mentioned in commit 9645d493