Convert string values to floating point, so that `number_format` method can properly format values.

Fixes #3687: Default `sourceLanguage` and `language` are now `en-US` in order for i18n formatter to work correctly

Fixes #3716: `DynamicModel::validateData()` does not call `validate()` if the `$rules` parameter is empty

Fixed the bug that requesting protected or private action methods would cause 500 error instead of 404

fixes #3539

fixes #3431

allow using it from the gridview directly

Adds support for timestamps beyond year 2038.