fixes #4045

issue #746

Translation review intro yii.md

issue #746

issue #746

fixes #4042

fixes #4047

issue #613

fixes #422

fixed some issues with schema detection

see https://github.com/yiisoft/yii2/commit/bf599b96bb47f006a0f6fb4859ead30648fc5dde

Fix #4018: sphinx db relation composite link

Fixes #2558: Enhanced support for memcached by adding `yii\caching\MemCache::persistentId` and `yii\caching\MemCache::options`

Gii `*Search` model generator fix

Http status codes are hardcoded in filter in debug

Manifest was not passed to view as was expected according to phpdoc.
We need it to extract status codes for filter.

Arbitrary http status codes are hardcoded in filter so it is impossible to search by status code not present in select.

Added support for transaction isolation levels

add translation for intro-upgrade-from-v1 [skip ci]

[ci skip]