Dashboards - add remove functionality

Summary: To get there, upgrade "headerless" to "headerMode". Add a new removepanel controller. Fixes T5084.

Test Plan: removed some panels to much success

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5078, T5084

Differential Revision: https://secure.phabricator.com/D9156

webroot/rsrc/js/application/dashboard/behavior-dashboard-async-panel.js

@@ -11,7 +11,8 @@ JX.behavior('dashboard-async-panel', function(config) {
 
   var data = {
     parentPanelPHIDs: config.parentPanelPHIDs.join(','),
-    headerless: config.headerless ? 1 : 0
+    headerMode: config.headerMode,
+    dashboardID: config.dashboardID
   };
 
   new JX.Workflow(config.uri)