Merge branch 'stable-2.15'
* stable-2.15:
AbstractElasticIndex: Don't mention "change" in exception message
Consistently import org.slf4j.LoggerFactory
PluginLoader: Make Logger private
Documentation: clarify latest IntelliJ version use
Elasticsearch builders: fix the Eclipse warnings
Remove stale references to no longer used jackson libraries
Add 'docker' tag to build rules for Elasticsearch tests
ReindexIT: Split Elasticsearch test out to a separate class
Change-Id: I1c11924d44c8fac18bba5aa4271d47aada851280