Merge branch 'stable-3.0'
* stable-3.0:
ChangeIndexer: Stop using deprecated Futures.immediateCheckedFuture
OutgoingEmail: Use UrlFormatter to get settings URL
CommentSender: Use UrlFormatter to get URLs for file and comments
Elasticsearch: Base the default number of shards on ES version
Disallow change index task duplication
AbstractPushForReview: Add tests for pushing with skip-validation option
Set version to 2.16.10-SNAPSHOT
Set version to 2.16.9
Documentation: Fix the Elasticsearch shards/replicas link
ProjectControl: Allow regexes ref strings for uploads
ProjectControl: Allow regexes ref strings for tags
ProjectControl: Reuse constants for ref strings
Add extension point to gr-user-header
Change-Id: Ib67847e1f8d972543b6b0491e270f6e501cc63b1