Fixes #4607: AR model will throw an exception if it does not have a primary key to avoid updating/deleting data massively

Updated yii.activeform.js to use the encode option introduced in #4122.
Updated ActiveForm with new option encodeErrorSummary

fixes #4690, close #4691

[ci skip]

Fix #4630: automatic generating of unique slug value to `yii\behaviors\Sluggable`

issue #4687

You can now customize test config without having uncommitted changes in
git.

issue #4687

Created ArrayCache class

[ci skip] Docs guide russian translation: translated rest-authentication.md into Russian

Fixes #4586: Signed bigint and unsigned int will be converted into integers when they are loaded from DB by AR

Conflicts:
	framework/CHANGELOG.md

also fixed an issue with default value loading of bool columns.

fixes #3489, fixes #4085, fixes #3920
related to #4672

fixes #4654

close #4655

`$config` can now be a closure that will have the `$configInstance` passed as the first param.

updated docs.

close #4656

Fixes #4122: `Html::error()` and `Html::errorSummary()` are now accepting `encode` option. If set to false it prevents encoding of error messages

- can be used to enable caching in a request without the need for any storage
- useful for example in complex console tasks that should still be independed

Fixes #4371: Active form client validation wasn't working in case of two models having same named fields

When rendering multiple models in the same ActiveForm if any of the field names in the two models is the same then the corresponding attribute in the yiiActiveForm object in yiiActiveForm.js (ie $('form').data('yiiActiveForm').attributes) of the first rendered model is overwritten by the attribute of the last model causing the client-side validation for the overwritten field not to run at all. Example: given two models Car and Owner with attributes {make, age} and {name, age} then if the Car is rendered first its age attribute will not have any client validation.