Allow resetting data and timestamps on TimeSeries

[rly]

Motivation

Partner PR to hdmf-dev/hdmf#868

TODO:

• Add tests
• Move validation to separate function that is called on build or into the setter (moving it into the setter would still not allow modifying multiple fields at once, e.g., changing TimeSeries with rate to having timestamps, but maybe that is OK for now)

How to test the behavior?

Currently without the validation safeguards, this is allowed:

from pynwb.testing.mock.base import mock_TimeSeries

ts = mock_TimeSeries(timestamps=[1,2,3,4], rate=None)
ts.rate = 5  # this works
ts.data = [2,3,4,5]
ts.timestamps = [1,2,3]

Checklist

• Did you update CHANGELOG.md with your changes?
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• Have you included the relevant issue number using "Fix #XXX" notation where XXX is the issue number? By including "Fix #XXX" you allow GitHub to close issue #XXX when the PR is merged.

[bendichter]

@rly I thought we agreed that this would be too flexible, because it would allow a user to take data and set it to None or replace a None with data, thus creating an invalid NWB file. Instead, we want to be able to get a new DataIO for data or timestamps. Let me see if I can create this feature

[CodyCBakerPhD]

@rly is this able to be closed? The set_data_io method does everything we need with regards to this issue