ES 5.x new features

Issue to track ES 5.x new features that may be useful. This may be helpful in determining when to switch to requiring ES 5.x as a minimum requirement.

Search_after [1].
This would allow cheaper scrolling. The GUI could potentially fetch only the results it needed to display/

Scripting [2]
ES now includes built-in secure scripting.

[1] https://www.elastic.co/guide/en/elasticsearch/reference/5.0/search-request-search-after.html

[2] https://www.elastic.co/guide/en/elasticsearch/reference/5.0/modules-scripting.html

Review the linked Elasticsearch search_after and scripting documentation, then inspect the GUI's current result-fetching and scrolling path. The issue names no files or tests and does not define a specific acceptance condition, so confirm which ES 5.x feature should be adopted and what behavior would mark it done.

Written by the indexing model from the issue text.