Allow for setting a cache namespace

If `cache_namespace` is set, `setNamespace` will be called on the resulting
cache instance if it is a Doctrine CacheProvider instance. Doctrine's
CacheProvider will take care of normalizing this call for various backends
based on its own rules.

    $app->register(
        new Dflydev\Silex\Provider\DoctrineOrm\DoctrineOrmServiceProvider,
        array(
            'orm.em.options' => array(
                'cache_namespace' => 'appname_',
                'metadata_cache' => 'apc',
                'query_cache'    => 'apc',
                'mappings' => array(
                    array(),
                ),
            ),
        )
    );

Thanks to @asiermarques for this work.

Closes #15
Closes #16

Author: simensen

src/Dflydev/Pimple/Provider/DoctrineOrm/DoctrineOrmServiceProvider.php

@@ -13,6 +13,7 @@
 
 use Doctrine\Common\Cache\ApcCache;
 use Doctrine\Common\Cache\ArrayCache;
+use Doctrine\Common\Cache\CacheProvider;
 use Doctrine\Common\Cache\MemcacheCache;
 use Doctrine\Common\Cache\MemcachedCache;
 use Doctrine\Common\Cache\XcacheCache;
@@ -192,7 +193,13 @@ public function register(\Pimple $app)
                 return $app[$cacheInstanceKey];
             }
 
-            return $app[$cacheInstanceKey] = $app['orm.cache.factory']($driver, $options[$cacheNameKey]);
+            $cache = $app['orm.cache.factory']($driver, $options[$cacheNameKey]);
+
+            if(isset($options['cache_namespace']) && $cache instanceof CacheProvider) {
+                $cache->setNamespace($options['cache_namespace']);
+            }
+
+            return $app[$cacheInstanceKey] = $cache;
         });
 
         $app['orm.cache.factory.backing_memcache'] = $app->protect(function() {