Merge branch 'stable-2.15'
* stable-2.15:
Set version to 2.14.13
Modify search autocompletion to include only email
ElasticContainer: Use Elasticsearch 5.6.12 for V5_6 tests
Add link to security documentation for Elasticsearch 6.4
Link to homepage for Elasticsearch compatibility
GerritServer#initAndStart: Remove unnecessary instantiation of Config
Revert "Suppress "unlikely argument type" warnings for IdString"
IdString: Don't compare equal to strings
Change-Id: I9b0db056eb4455a7c430779c6e8666bd770da072