Add the use of the constant FTP_* in config for FTP transfer mode and add doc for FTP Adapter

DependencyInjection/Factory/FtpAdapterFactory.php

@@ -52,7 +52,12 @@ class FtpAdapterFactory implements AdapterFactoryInterface
                 ->scalarNode('password')->defaultNull()->end()
                 ->booleanNode('passive')->defaultFalse()->end()
                 ->booleanNode('create')->defaultFalse()->end()
-                ->scalarNode('mode')->defaultValue(FTP_ASCII)->end()
+                ->scalarNode('mode')
+                    ->defaultValue(FTP_ASCII)
+                    ->beforeNormalization()
+                    ->ifString()
+                    ->then(function($v) { return constant($v); })
+                ->end()
             ->end()
         ;
     }

README.markdown

@@ -284,3 +284,34 @@ knp_gaufrette:
 ```
 
 [gaufrette-homepage]: https://github.com/KnpLabs/Gaufrette
+
+## Ftp
+
+Adapter for FTP.
+
+### Parameters
+
+ * `directory` The directory of the filesystem *(required)*
+ * `host` FTP host *(required)*
+ * `username` FTP username *(default null)*
+ * `password` FTP password *(default null)*
+ * `port` FTP port *(default 21)*
+ * `passive` FTP passive mode *(default false)*
+ * `create` Whether to create the directory if it does not exist *(default false)*
+ * `mode` FTP transfer mode *(defaut FTP_ASCII)*
+
+### Example
+
+``` yaml
+# app/config/config.yml
+knp_gaufrette:
+    adapters:
+        foo:
+            ftp:
+                host: example.com
+                username: user
+                password: pass
+                directory: /example/ftp
+                create: true
+                mode: FTP_BINARY
+```