[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/ExportInterface.php

@@ -13,6 +13,7 @@ namespace Chill\MainBundle\Export;
 
 use Doctrine\ORM\NativeQuery;
 use Doctrine\ORM\QueryBuilder;
+use Symfony\Component\Form\FormBuilderInterface;
 
 /**
  * Interface for Export.
@@ -28,6 +29,16 @@ use Doctrine\ORM\QueryBuilder;
  */
 interface ExportInterface extends ExportElementInterface
 {
+    /**
+     * Add a form to collect data from the user.
+     */
+    public function buildForm(FormBuilderInterface $builder);
+
+    /**
+     * Get the default data, that can be use as "data" for the form
+     */
+    public function getFormDefaultData(): array;
+
     /**
      * Return which formatter type is allowed for this report.
      *