Fix table name in yii\rbac\DbManager::$itemChildTable

* 'master' of github.com:yiisoft/yii2:
  Added link to pull requesting guide

thanks to @chris68 PR #1338

Changelog for #1852

gii additional table prefix fixes

[WIP] ActiveRecord::tableName() hardcoded prefix fix

UplodedFile enhasement

fix russian messages.

Removed error-block HTML class and related styles and used Bootstrap3 standard practice about errors instead

Add pt-BR translated messages