Edit Dashboard title and Slice title in place (#2940)

* Edit Dashboard title and Slice title in place

Add EditableTitle component into Dashboard and Explore view to support edit title inline.

superset/assets/javascripts/dashboard/Dashboard.jsx

@@ -341,6 +341,10 @@ export function dashboardContainer(dashboard, datasources, userid) {
         },
       });
     },
+    updateDashboardTitle(title) {
+      this.dashboard_title = title;
+      this.onChange();
+    },
   });
 }