More specific entwine rule for delete alert in GridField

The rule didn't apply in Firefox because of how it handles specificity,
so made it a bit more specific (added "button" and ".action")

admin/javascript/LeftAndMain.EditForm.js

@@ -200,6 +200,15 @@
 			 * Function: onclick
 			 */
 			onclick: function(e) {
+				// Confirmation on delete. 
+				if(
+					this.hasClass('gridfield-button-delete')
+					&& !confirm(ss.i18n._t('TABLEFIELD.DELETECONFIRMMESSAGE'))
+				) {
+					e.preventDefault();
+					return false;
+				}
+
 				if(!this.is(':disabled')) {
 					this.parents('form').trigger('submit', [this]);
 				}

forms/gridfield/GridFieldDetailForm.php

@@ -349,7 +349,7 @@ class GridFieldDetailForm_ItemRequest extends RequestHandler {
 			if($canDelete) {
 				$actions->push(FormAction::create('doDelete', _t('GridFieldDetailForm.Delete', 'Delete'))
 					->setUseButtonTag(true)
-					->addExtraClass('ss-ui-action-destructive'));
+					->addExtraClass('ss-ui-action-destructive action-delete'));
 			}
 
 		}else{ // adding new record

javascript/GridField.js

@@ -135,7 +135,8 @@
 			}
 		});
 
-		$('.ss-gridfield .action.gridfield-button-delete, .cms-content-actions .ss-ui-action-destructive .ui-button-text').entwine({
+		// Covers both tabular delete button, and the button on the detail form 
+		$('.ss-gridfield .Actions .action.gridfield-button-delete, .cms-edit-form .Actions button.action.action-delete').entwine({
 			onclick: function(e){
 				if(!confirm(ss.i18n._t('TABLEFIELD.DELETECONFIRMMESSAGE'))) {
 					e.preventDefault();