Added support for relation by array attributes

fixes #1249
added elasticsearch test case for array attribute relations
fixed issue with indexBy and array valued relations
add support for array valued attr relations to unlink and link
Update CHANGELOG.md
Merge branch 'master' into array-attribute-relations

* master:
  Update output-data-widgets.md
  Fixes #4370: fileinfo extension is required for FileValidator.
  Fixes #4342
  Fixes #3887
  minor refactoring of FileValidator.
  Doc translate for rest-resources
  Better fix for Dropdown container options
  #4388: CORS filter fixes:
  Fixed test break.
  #4310: Removed `$data` from signature of `yii\rbac\ManagerInterface`
  Update .travis.yml
  Update ActiveRecordInterface.php
  Fixes #4384.
  Sphinx distributed indexes support provided
  typo fix [skip ci]
  Fixes #3611: Refactored query caching.
Merge pull request #4380 from yiisoft/array-attribute-relations

Array attribute relations