Add periodic tests for yaspgrid
We merged !3 (merged), but Dominik suggested to add additional tests for periodic yaspgrid. These are currently in the code, but not enable, as something (please ask @dominic) still needs to be cleaned up.
We merged !3 (merged), but Dominik suggested to add additional tests for periodic yaspgrid. These are currently in the code, but not enable, as something (please ask @dominic) still needs to be cleaned up.