Add 'Save and stay' button on missing pages at back office

controllers/admin/AdminSpecificPriceRuleController.php

@@ -285,6 +285,15 @@ class AdminSpecificPriceRuleControllerCore extends AdminController
             'submit' => array(
                 'title' => $this->l('Save')
             ),
+            'buttons' => array(
+                'save-and-stay' => array(
+                    'title' => $this->l('Save and stay'),
+                    'name' => 'submitAdd'.$this->table.'AndStay',
+                    'type' => 'submit',
+                    'class' => 'btn btn-default pull-right',
+                    'icon' => 'process-icon-save',
+                ),
+            ),
         );
         if (($value = $this->getFieldValue($this->object, 'price')) != -1) {
             $price = number_format($value, 6);