Refactored ActiveQuery::one() to be consistent with all() creation

Added tests that are making sure Gii isn't failing with errors

- Enh #4520: yii\caching/MemCache.php add sasl support (xjflyttp)

Fix signature validation

as it is in RC phase now we should be able to report bugs if they occur.

Fix Russian translation

Fixes #4497: Bad Request, Unable to verify your data submission

Update intro-upgrade-from-v1.md

Fixes #4519: `yii\base\Model::isAttributeRequired()` should check if the `when` option of the validator is set

[Uk][Guide] Add pages translation

Improved checks where substr_compare is used, replaced more substr + comapre cases with substr_compare

This reverts commit 07f01bcf.

BUT ONLY for the /build directory!