[WIP] Add/zarrio

[oruebel]

This PR is a draft and has been created to ease sharing and discussion. It is not intended for active use.

Motivation

Integrate HDMF ZarrIO backend with PyNWB and enable integration testing with ZarrIO

How to test the behavior?

Run the integration tests

Checklist

• Have you checked our Contributing document?
• Have you ensured the PR description clearly describes problem and the solution?
• Is your contribution compliant with our coding style ? This can be checked running flake8 from the source directory.
• Have you checked to ensure that there aren't other open Pull Requests for the same change?
• Have you included the relevant issue number using #XXX notation where XXX is the issue number ?

[oruebel]

Zarr I/O is part of the hdmf-zarr package https://hdmf-zarr.readthedocs.io