Modify Ketos annotation table format?

A while back the Ketos format for selection tables was modified to accommodate selections that span multiple audio files. Specifically, the new format used a Selection ID as primary index and the filename as secondary index. This is document in the docstring of the selection_table.py module:

https://git-dev.cs.dal.ca/meridian/ketos/-/blob/master/ketos/data_handling/selection_table.py

However, the Ketos format for annotation tables still uses the "old" style where filename is used as primary index and and Annotation ID as secondary index.

@padovese , @frazao Should we consider updating the Ketos annotation table format to be aligned with the Selection table format? (I think so!)