Fix bug in PathLikeSelector._index_row_in().
Add unit test for Pattern.split_multiindex().
Fix handling of selectors with a single level.
Fix handling of single-level selectors in Interface class, update unit tests.
Merge branch 'port_ids' of https://github.com/neurokernel/neurokernel

Bug fix
Added video support and made selectors flat for faster simulation (video recording of output does not work yet but maybe it is because of external factors)