FIX: Get CMS preview working for non inline-editable elements. (silve…

…rstripe#936)

Fixes silverstripe#905. Depends on silverstripe/silverstripe-admin#1250
This was a feature in an earlier version of the module and most of the code is still in place.

src/Models/BaseElement.php

@@ -31,6 +31,7 @@
 use SilverStripe\View\ArrayData;
 use SilverStripe\View\Parsers\URLSegmentFilter;
 use SilverStripe\View\Requirements;
+use SilverStripe\ORM\CMSPreviewable;
 
 /**
  * Class BaseElement
@@ -47,7 +48,7 @@
  *
  * @mixin Versioned
  */
-class BaseElement extends DataObject
+class BaseElement extends DataObject implements CMSPreviewable
 {
     /**
      * Override this on your custom elements to specify a CSS icon class
@@ -113,6 +114,10 @@ class BaseElement extends DataObject
      */
     protected $controller;
 
+    private static $show_stage_link = true;
+
+    private static $show_live_link = true;
+
     /**
      * Cache various data to improve CMS load time
      *