Summary of changes

• Added the optional stimulus_template column to IntracellularStimuliTable. The purpose of this column is to store stimulus template waveforms, i.e. waveforms that were not recorded, but were defined as protocols in the recording software.
  From the perspective of writing analysis tools, it is much easier to analyze recordings if this noiseless version of the stimulus is available.

Checklist

For all schema changes:

• Add release notes for the PR to docs/format/source/format_release_notes.rst.

If this is the first schema change after a schema release (i.e., the version string in core/nwb.namespace.yaml does not
end in "-alpha"), then:

• Update the version string in core/nwb.namespace.yaml and core/nwb.file.yaml to the next major/minor/patch
  version with the suffix "-alpha". For example, if the current version is 2.4.0 and this is a minor change, then the
  new version string should be "2.5.0-alpha".
• Update the value of the version variable in docs/format/source/conf.py to the next version without the
  suffix "-alpha", e.g., "2.5.0".
• Update the value of the release variable in docs/format/source/conf.py to the next version with the suffix
  "-alpha", e.g., "2.5.0-alpha".
• Add a new section in the release notes docs/format/source/format_release_notes.rst for the new version
  with the date "Upcoming" in parentheses.