Merge branch '2.7' into 2.8

* 2.7: (28 commits)
  [Process] Use stream based storage to avoid memory issues
  Fix upgrade guides concerning erroneous removal of assets helper
  [Process] Remove a misleading comment
  Fix markdown typo
  ChooseBaseUrl should return an index
  [Form] ChoiceType: Fix a notice when 'choices' normalizer is replaced
  Improve the phpdoc of SplFileInfo methods
  [Process] Use stream based storage to avoid memory issues
  [FrameworkBundle] Don't log twice with the error handler
  Remove useless is_object condition
  [Process] Fix typo, no arguments needed anymore
  [Serializer] Introduce constants for context keys
  Fixed the documentation of VoterInterface::supportsAttribute
  Fixed Bootstrap form theme form "reset" buttons
  Remove useless duplicated tests
  [FrameworkBundle] Optimize framework extension tests
  synchronize 2.7 and 3.0 upgrade files
  fix merge 2.3 into 2.7 for SecureRandom dependency
  Use is_subclass_of instead of reflection
  Use is_subclass_of instead of Reflection when possible
  ...

Author: fabpot

SplFileInfo.php

@@ -38,6 +38,8 @@ public function __construct($file, $relativePath, $relativePathname)
     /**
      * Returns the relative path.
      *
+     * This path does not contain the file name.
+     *
      * @return string the relative path
      */
     public function getRelativePath()
@@ -48,6 +50,8 @@ public function getRelativePath()
     /**
      * Returns the relative path name.
      *
+     * This path contains the file name.
+     *
      * @return string the relative path name
      */
     public function getRelativePathname()