minor #1043 Fixed Form Provider documentation (WouterJ)

This PR was submitted for the master branch but it was merged into the 1.2 branch instead (closes #1043).

Discussion
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Fixed Form Provider documentation

The Locale component is replaced by the Intl and Icu components, which are taken care of by Composer.

The twig bridge also does not work without translation, as far as I tested.

Commits
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dddd0aab Fixed Form Provider documentation

doc/providers/form.rst

@@ -68,15 +68,6 @@ Registering
             "symfony/config": "~2.3",
             "symfony/translation": "~2.3"
         }
-
-    The Symfony Form Component relies on the PHP intl extension. If you don't have
-    it, you can install the Symfony Locale Component as a replacement:
-
-    .. code-block:: json
-
-        "require": {
-            "symfony/locale": "~2.3"
-        }
         
     The Symfony Security CSRF component is used to protect forms against CSRF attacks:
 
@@ -86,13 +77,15 @@ Registering
             "symfony/security-csrf": "~2.4"
         }
 
-    If you want to use forms in your Twig templates, make sure to install the
-    Symfony Twig Bridge:
+    If you want to use forms in your Twig templates, you can also install the
+    Symfony Twig Bridge. Make sure to install, if you didn't do that already,
+    the Translation component in order for the bridge to work:
 
     .. code-block:: json
 
         "require": {
-            "symfony/twig-bridge": "~2.3"
+            "symfony/twig-bridge": "~2.3",
+            "symfony/translation": "~2.3"
         }
 
 Usage