Provide integration test for grid io #586
Description
With the current issue #582 it became apparent that sinks and sources for PSDM data are not necessarily always compatible, i.e. a sink producing output that cannot be read by a corresponding source.
To further investigate such cases and prevent them from happening in the future, an integration test should be provided that writes out an example grid, reads it back in (or vice-versa) and compares results.