Changed csrf-var to csrf-param

gridview header/footer fix

Some missing base unit tests

Changed csrf-var to csrf-param due to meta validation error. The validation error as mentioned in the issue https://github.com/yiisoft/yii2/issues/2363. It is fixed in this pull request.

When translation is missing source language should be used for formatting

This reverts commit c94131b8.

fixed configs

check error level in error handler

Update error.md

typo fix

Fixes #2054: Added support for using custom application configuration with the console command runner

need to confirm the exception properties in Yii 2