added some tests for Url helper
Added key param to ActionColumn button Closure

fixes #4602, close #4624
Added null AR relation test for Twig extension
Fix for #2925 and #4290 (Twig does not properly support null attribute and relationship values)
Support for method calls on models from Twig templates
Fixes #4290: Fixed throwing exception when trying to access AR relation that is null
fixed typo
Fixes #4592: Fixed `yii help` command was listing incorrect action names for methods like `actionSayNO`
Merge pull request #4629 from xBazilio/patch-6

fixed typo
Fixes #4595: more consistend use of "false" in "don't use" case
More cases for #4595
Removed index-test from codeception instructions since it's used automatically
Merge branch 'master' of github.com:yiisoft/yii2
add start-databases.md
Grammar fix
Merge pull request #4639 from RichWeber/master

[ci skip][Uk][Guide] Add page translation
Fixes #4622: Simplified the way of creating a Faker fixture template file
minor refactoring. [skip ci]
Fixed condition for #4595
Grammar fixes