Fix not-working (?) tests using GridTestData #79
Description
transformerCtoG in GridTestData had a wrong node in the test data (was nodeF instead of nodeG). I changed this, but strangely(?) all tests are still passing. This could indicate that a) either one of the tests is not checking grid extraction properly or b) there is something broken with the logic of grid disassembling as this test data is also used for grid disassembling.
This needs to be investigated carefully the ensure that everything works correctly. Additionally, I would recommend to extend the tests that they break if nodes are not set correctly!