allow using it from the gridview directly

Adds support for timestamps beyond year 2038.

InvalidCallException, InvalidParamException, UnknownMethodException are now extended from SPL BadMethodCallException

Adjustments code according to the standards.
Adding missing PHPDoc comment.

Fixes #3121: `yii\base\Application::bootstrap` may fail to load some components if they are specified as class names

Fixes #3091: Fixed inconsistent treatment of `Widget::run()` when a widget is used as a container and as a self-contained object

issue #3026

fixes #3034

Improved action filter and action execution flow by supporting installing action filters at controller, module and application levels

Added support to allow an event handler to be inserted at the beginning of the existing event handler list

Fixed phpdoc, removed unit tests for Formatter asRelativeTime that were relative to current time since it was impossible to specify correct expected values

fixes #1946