(into master) Bug 986521 -  Fetch Directory Links data from a network location to cache locally
Enable directory links download and file cache
(into bug986521) Bug 993904 - Use cached directory links instead of locally packaged links
Refactor DirectoryLinksProvider to getLinks from file cached in profile directory.
Change test accordingly
Test corrupted json cache file.
Rename function for consistency.
Unify test provider creation and cleanup.
Clean merge conflict
Remove unused code