[Validator] Backported constraint validator tests from 2.5
Merge branch '2.3' into 2.4

* 2.3:
  [Validator] Backported constraint validator tests from 2.5
  Fix toolbar vertical alignment.
  [HttpFoundation] MongoDbSessionHandler supports auto expiry via configurable expiry_field
  [FrameworkBundle] add missing attribute to XSD
  Allow basic auth in url. Improve regex. Add tests.
  fix typos and syntax in Profiler controller method comments
  remove volatile tests
  [Console] fixed style creation when providing an unknown tag option
  [Validator] Convert objects to string in comparison validators. Reapplies 6cf5e0812e6f20d60acbc0324abf96475e89b6ef
  [HttpFoundation] Update QUERY_STRING when overrideGlobals

Conflicts:
	src/Symfony/Bridge/Doctrine/Tests/Validator/Constraints/UniqueValidatorTest.php
	src/Symfony/Component/HttpFoundation/Tests/RequestTest.php
	src/Symfony/Component/Validator/Constraints/AllValidator.php
	src/Symfony/Component/Validator/Constraints/CollectionValidator.php
	src/Symfony/Component/Validator/Tests/Constraints/AbstractComparisonValidatorTestCase.php
	src/Symfony/Component/Validator/Tests/Constraints/CallbackValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/EqualToValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/FileValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/GreaterThanValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/IdenticalToValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/ImageValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/LessThanOrEqualValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/LessThanValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/NotEqualToValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/NotIdenticalToValidatorTest.php
	src/Symfony/Component/Validator/Tests/Constraints/UrlValidatorTest.php
Fixed #11675 ValueToDuplicatesTransformer accept "0" value

Fixed wrong return null syntax

Added transformation to null on empty arrays

Removed useless statement in condition and switched to yoda condition
Merge branch '2.3' into 2.4

* 2.3:
  [DependencyInjection] fix @return anno created by PhpDumper
  Fixed the phpdoc of the VoterInterface
  [DoctrineBridge] Fix empty parameter logging in the dbal logger
  Fixed #11675 ValueToDuplicatesTransformer accept "0" value
  check for the correct field type
  fix handling of nullable XML attributes
  [DomCrawler] fix the axes handling in a bc way

Conflicts:
	src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php
Merge branch '2.4' into 2.5

* 2.4:
  [DependencyInjection] fix @return anno created by PhpDumper
  Fixed the phpdoc of the VoterInterface
  [DoctrineBridge] Fix empty parameter logging in the dbal logger
  Fixed #11675 ValueToDuplicatesTransformer accept "0" value
  check for the correct field type
  fix handling of nullable XML attributes
  [DomCrawler] fix the axes handling in a bc way

Conflicts:
	src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9.php
	src/Symfony/Component/DependencyInjection/Tests/Fixtures/php/services9_compiled.php