Update TimeIntervals.timeseries to use new TimeSeriesReferenceVectorData

[oruebel]

Motivation

#470 added the new TimeSeriesReferenceVectorData type. This PR updates TimeIntervals to use the new TimeSeriesReferenceVectorData type. This does not alter the overall structure of TimeIntervals in a major way aside from changing the value of the neurodata_type attribute in the file from VectorData to TimeSeriesReferenceVectorData. This change replaces the existing TimeIntervals.timeseries column with a TimeSeriesReferenceVectorData type column of the same name and overall schema. This change facilitate creating common functionality around TimeSeriesReferenceVectorData. This change affects all existing TimeIntervals tables as part of the intervals/ group, i.e., intervals/epochs, intervals/trials, and intervals/invalid_times (#470)

Summary of changes

• Update TimeIntervals to use the new TimeSeriesReferenceVectorData type

Relates PRs

NeurodataWithoutBorders/pynwb#1390 is the matching PR on PyNWB for this

PR checklist for schema changes

• Update the version string in docs/format/source/conf.py, core/nwb.namespace.yaml, and /core/nwb.file.yaml
  to the next version with the suffix "-alpha"
• Add a new section in the release notes for the new version with the date "Upcoming"
• Add release notes for the PR to docs/format/source/format_release_notes.rst

[rly]

Looks good. Please update the version strings in docs/format/source/conf.py, core/nwb.namespace.yaml, and /core/nwb.file.yaml to "2.5.0-alpha"

[rly]

Looks good. Feel free to squash and merge.

[CodyCBakerPhD]

Would this sort of reference object make sense to use for waveform columns on a UnitsTable? We often have difficulty getting the properties of that column to properly match TimeSeries-like attributes. What do you think @oruebel @bendichter

This change facilitate creating common functionality around TimeSeriesReferenceVectorData. This change affects all existing TimeIntervals tables as part of the intervals/ group, i.e., intervals/epochs, intervals/trials, and intervals/invalid_times

Would it also apply to custom TimeInterval table objects placed in, say, a 'processing' module?

[oruebel]

Would it also apply to custom TimeInterval table objects placed in, say, a 'processing' module?

Yes, this updates the TimeIntervals type and as such will affect all TimeIntervals tables

Would this sort of reference object make sense to use for waveform columns on a UnitsTable?

I'm not sure. This would require storing the waveforms in (likely many individual) TimeSeries and then referencing subsets of those TimeSeries. I'm not sure how well this would work here, in particular, I'm not sure about how many different TimeSeries objects would be required and what the performance for accessing the data would end up being as it will required resolving a lot of links.