Fix for #4372
Doc update [skip ci]
Changelog update [skip ci]
Merge with master
Added bower.json for gii and debug extensions.
Update structure-widgets.md

changed bootstrap namespace to jui
Merge pull request #4726 from xskif/patch-1

[skip-ci] Update structure-widgets.md
Removed bogus conditional
CacheFilter test coverage
Fix for `@covers` annotations
Fixes #4727: Fixed wrong Stylus definition in `\yii\web\AssetConverter`
Merge pull request #4728 from DaSourcerer/4372-httpcache-rfc7232-compliance

RFC 7232 Compliance for yii\filters\HttpCache
Added missing github name to changelog
Additional fix to #4728.
Additional fix to #4728.