[DependencyInjection] fixed a bug in the YAML dumper where references where not converted to the @ notation
Merge branch '2.0' into 2.1

* 2.0:
  [Yaml] fixed unneeded BC break
  [DependencyInjection] fixed a bug in the YAML dumper where references where not converted to the @ notation
  [Yaml] fixed typo
  updated VERSION for 2.0.22
  update CONTRIBUTORS for 2.0.22
  updated CHANGELOG for 2.0.22

Conflicts:
	src/Symfony/Component/HttpKernel/Kernel.php