Scroll export

[fnocetti]

fixes #2924

PR checklist:

• Update READ.me ?
• Update API documentation ?

QA checklist:

• Smoke test the functionality described in the issue
• Test for side effects
• UI responsiveness
• Cross browser testing
• Code review

[fnocetti]

This PR includes a proof of concept of using the Scroll API from elastic to export more than 10k results.
It implements a scroll method in the search module that returns an iterator. That iterator is then used in the csv exporter module.
To continue this work, testing needs to be taken care of.
If there was a need to consume all of the results at once, an all method could be included into the iterator that leverages the next and hasNext methods of itself to list every result.