Boost based on the currently selected locale.
Merge branch 'master' into search-translated-articles
refer to English via a setting
Merge branch 'master' into search-translated-articles
Add search section to 'Site Operations' section.
Store information about the parent document for translated docs.

- Show the parent in the search results.
- Introduce a SiteURLField to simplify rendering it.
- Reindex all translations of a document whenever a doc is rendered.
Use 4 threads to run the celery tasks.
Merge branch 'master' into search-translated-articles
Fix the filtering to do the follwing:

- when in English only show English documents
- when in non-English mode show both language documents as well as English
Reverted some previously removed parts of the result template to better work with the new search method.
Restored some missing code and clarified some other.
Commented in logging setting for elasticsearch again.
Revert log level.
Make the branch work in prod without breaking.
Merge pull request #2368 from jezdez/search-translated-articles

Boost based on the currently selected locale.