minor #10911 [Form] Composer dependencies (csarrazi)

This PR was merged into the 2.4 branch.

Discussion
----------

[Form] Composer dependencies

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| License       | MIT
| Doc PR        | -

Right now, launching tests from the Form component's directory doesn't work, due to missing dev dependencies. This should be merged back into master afterwards.

Also fixed a problem related to a bad method signature in ```Symfony\Component\Form\Tests\Extension\DataCollector\FormDataExtractorTest_SimpleValueExporter```

Commits
-------

7b5857c Fixed FormDataExtractorTest_SimpleValueExporter::exportValue not implementing the interface correctly
e4fa5d8 Updated form dev dependencies

src/Symfony/Component/Form/Tests/Extension/DataCollector/FormDataExtractorTest.php

@@ -25,7 +25,7 @@ class FormDataExtractorTest_SimpleValueExporter extends ValueExporter
     /**
      * {@inheritdoc}
      */
-    public function exportValue($value)
+    public function exportValue($value, $depth = 1, $deep = false)
     {
         return var_export($value, true);
     }

src/Symfony/Component/Form/composer.json

@@ -25,7 +25,9 @@
     "require-dev": {
         "symfony/validator": "~2.2",
         "symfony/http-foundation": "~2.2",
-        "symfony/security-csrf": "~2.4"
+        "symfony/http-kernel": "~2.4",
+        "symfony/security-csrf": "~2.4",
+        "doctrine/collections": "~1.0"
     },
     "suggest": {
         "symfony/validator": "For form validation.",