Check availabilty field in BaseActiveRecord::populateRecord

check with Object::canSetProperty()

fixes #4305, close #4211
Better Windows detection
Improved strtr calls
Better Windows detection
Used substr_compare instead of substr when we don't care about result
Avoid method call in for condition
Added info about running codeception tests to getting-started
Add References Badge to Readme
Added test-overview
Adjusted docs to use global phpunit and codeception installation
Merge pull request #4411 from reiz/master

Add References Badge to Readme
Added note about app templates
Very draft testing docs
Fixes #4409: Upper case letters in subdirectory prefixes of controller IDs were not properly handled
Added client-side file validator
Fixed typo and inconsistent conditionals
Changed Array.prototype.slice.call() into jQuery's $.each function for consistency
Fixes #4360: Added client validation support for file validator
\yii\behaviors\AttributeBehavior updated
\yii\behaviors\BlameableBehavior updated