Merge branch '2.0' into 2.1

* 2.0:
  updated license year
  Update src/Symfony/Component/HttpFoundation/Response.php
  [Console] fixed unitialized properties (closes #5935)
  [Bundle] [FrameworkBundle] fixed typo in phpdoc of the SessionListener.
  bumped Symfony version to 2.0.21-DEV
  updated VERSION for 2.0.21
  updated CHANGELOG for 2.0.21

Conflicts:
	src/Symfony/Bundle/SwiftmailerBundle/LICENSE
	src/Symfony/Component/Filesystem/LICENSE
	src/Symfony/Component/HttpFoundation/Response.php
	src/Symfony/Component/HttpKernel/Kernel.php