Tests for functionality in util-networks-misc.R

[bockthom]

At the moment, we don't have tests for the functionality that is contained in util-networks-misc.R (e.g., retrieving expanded adjacency matrices, converting them to arrays, etc.). Parts of this functionality are used in the showcase.R, that is, we would see potential errors that are thrown during the run of showcase.R, but we don't test for the correctness of the functionality yet.

To make sure that the functionality is implemented correctly and to be able to spot deviations from the expected behavior when new package versions of package Matrix are released, it would be really helpful to have tests for the functionality that is contained in util-networks-misc.R.