Split YaspGrid tests into more tests and introduce parallel testing
The previous YaspGrid test was a single test which took ages to compile and run.
This branch remodels the Yasp testing suite to achieve the following:
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Split the different parts into separate tests -
Introduce a more sophisticated communication test -
Test periodic grids -
Do parallel testing through dune_add_test -
Test with -Wall -Werror!!! -
Have tests with and without deprecations!