Update Neo integration for NWB support

[ilkilic]

This PR updates NEO integration to support NWB formats and introduces a new example that demonstrate how to load data with NEO.

Checklist:

• Unit tests are added to cover the changes (skip if not applicable).
• The changes are mentioned in the documentation (skip if not applicable).
• CHANGELOG file is updated (skip if not applicable).

[anilbey]

Thanks, looks great.

Could you address the following also:

• the name of the example can be more explicit perhaps nwb-via-neo or load-nwb or something similar
• If possible, in the notebook besides the interspike interval, could you show at least one other feature? The sonata-network notebook is also showing the interspike interval feature. Some different feature/features would be good to show on the experimental data. E.g. perhaps some burst related feature as Rajnish mentioned. cc @darshanmandge which features may be suited for this experimental NWB
• Could you modify the docs/examples_to_rst.sh script @AurelienJaquier had created to make sure this notebook will be rendered in the docs?

[darshanmandge]

Thanks @ilkilic ! You can use this burst related features: spikes_per_burst, strict_burst_number, strict_burst_mean_freq

[ilkilic]

I have made the requested changes in the latest commits

[anilbey]

Wow looks so good, thanks a lot @ilkilic