feature #964 Allowed shared ContextListener for firewalls (ibrasho)

This PR was squashed before being merged into the 2.0.x-dev branch (closes #964).

Discussion
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Allowed shared ContextListener for firewalls

In response to #963.

Checks for a `context` key in the firewall configuration, if it's not there use `name`.

Commits
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a56d0fa4 Allowed shared ContextListener for firewalls

src/Silex/Provider/SecurityServiceProvider.php

@@ -171,7 +171,8 @@ class SecurityServiceProvider implements ServiceProviderInterface, EventListener
                 $users = isset($firewall['users']) ? $firewall['users'] : array();
                 $security = isset($firewall['security']) ? (bool) $firewall['security'] : true;
                 $stateless = isset($firewall['stateless']) ? (bool) $firewall['stateless'] : false;
-                unset($firewall['pattern'], $firewall['users'], $firewall['security'], $firewall['stateless']);
+                $context = isset($firewall['context']) ? $firewall['context'] : $name;
+                unset($firewall['pattern'], $firewall['users'], $firewall['security'], $firewall['stateless'], $firewall['context']);
 
                 $protected = false === $security ? false : count($firewall);
 
@@ -187,7 +188,7 @@ class SecurityServiceProvider implements ServiceProviderInterface, EventListener
                     }
 
                     if (false === $stateless) {
-                        $listeners[] = 'security.context_listener.'.$name;
+                        $listeners[] = 'security.context_listener.'.$context;
                     }
 
                     $factories = array();