Minor fixes
add caching-data.md
Merge remote-tracking branch 'upstream/master' into upstream

* upstream/master:
  gridview and listview use widget ID in base tag
  typo fix [skip ci]
  Update CHANGELOG.md
  made elasticsearch error messages more readable
  Spanish structure-views [skip ci]
  Fix filename
  Update README.md
  https://github.com/yiisoft/yii2/pull/4091#discussion_r14296860
  Fix possibility of non-removed symlinked directory.
  Fixed typo. [skip ci]
  changed default for rotateByCopy of FileTarget