* upstream: (35 commits)
  Fixes #1691: added “viewport” meta tag to layout views.
  Fixed the issue that query cache returns the same data for the same SQL but different query methods
  moved section
  subsection added
  typo [skip ci]
  docs about response
  Fixes #1586: `QueryBuilder::buildLikeCondition()` will now escape special characters and use percentage characters by default
  docs improved
  csrf docs added
  Fixes #1685: UrlManager::showScriptName should be set true for tests.
  Fixes #1688: ActiveForm is creating duplicated messages in error summary
  change back the visibility of findTableNames to protected.
  Typo fix.
  Fixes #1681: Added support for automatically adjusting the "for" attribute of label generated by `ActiveField::label()`
  Simplified tests.
  Fixes #1631: Charset is now explicitly set to UTF-8 when serving JSON
  Fixed typo
  added html layout for mail component in basic app
  CS fixes.
  Merge branch 'debug_module_improvements' of github.com:Ragazzo/yii2 into Ragazzo-debug_module_improvements
  ...