Update documentation. Add doctrine usage.

README.markdown

@@ -696,4 +696,35 @@ data://backup/...
 data://pictures/...
 ```
 
+## Doctrine DBAL (doctrine_dbal)
+
+Adapter that allows you to store data into a database.
+
+### Parameters
+
+ * `connection_name` The doctrine dbal connection name like `default`
+ * `table` The table name like `media_data`
+ * `key`: The primary key in the table
+ * `content`: The field name of the file content
+ * `mtime`: The field name of the timestamp
+ * `checksum`: The field name of the checksum
+
+### Example
+
+``` yaml
+# app/config/config.yml
+knp_gaufrette:
+    adapters:
+        database:
+            doctrine_dbal:
+                connection_name: default
+                table: data
+                columns:
+                    key: id
+                    content: text
+                    mtime: date
+                    checksum: checksum
+```
+
 [gaufrette-homepage]: https://github.com/KnpLabs/Gaufrette
+