[edit export] add required method on export's interface

The method "getFormDefaultData" is applyied on every interface which
will use it:

- ExportInterface
- AggregatorInterface
- DirectExportInterface
- FilterInterface

The method buildForm is moved to those interfaces.

[ci-skip]

src/Bundle/ChillMainBundle/Export/FormatterInterface.php

@@ -34,6 +34,11 @@ interface FormatterInterface
         array $aggregatorAliases
     );
 
+    /**
+     * get the default data for the form build by buildForm
+     */
+    public function getFormDefaultData(array $aggregatorAliases): array;
+
     public function getName();
 
     /**