Fix Fluent interface on mapper

Datagrid/DatagridMapper.php

@@ -101,11 +101,13 @@ class DatagridMapper
 
     /**
      * @param string $key
-     * @return void
+     * @return \Sonata\AdminBundle\Datagrid\DatagridMapper
      */
     public function remove($key)
     {
         $this->admin->removeFilterFieldDescription($key);
         $this->datagrid->remove($key);
+
+        return $this;
     }
 }

Datagrid/ListMapper.php

@@ -95,7 +95,7 @@ class ListMapper
 
     /**
      * @param  string $key
-     * @return void
+     * @return \Sonata\AdminBundle\Datagrid\ListMapper
      */
     public function remove($key)
     {

Form/FormMapper.php

@@ -133,12 +133,14 @@ class FormMapper
 
     /**
      * @param string $key
-     * @return void
+     * @return \Sonata\AdminBundle\Form\FormMapper
      */
     public function remove($key)
     {
         $this->admin->removeFormFieldDescription($key);
         $this->formBuilder->remove($key);
+
+        return $this;
     }
 
     /**

Show/ShowMapper.php

@@ -103,12 +103,14 @@ class ShowMapper
 
     /**
      * @param string $key
-     * @return void
+     * @return \Sonata\AdminBundle\Show\ShowMapper
      */
     public function remove($key)
     {
         $this->admin->removeShowFieldDescription($key);
         $this->list->remove($key);
+
+        return $this;
     }
 
     /**