feat(panel): disable span options in fullscreen

closes #4018

public/app/features/panel/panel_menu.js

@@ -35,8 +35,10 @@ function (angular, $, _) {
         if (ctrl.dashboard.meta.canEdit) {
           template += '<div class="panel-menu-inner">';
           template += '<div class="panel-menu-row">';
-          template += '<a class="panel-menu-icon pull-left" ng-click="ctrl.updateColumnSpan(-1)"><i class="fa fa-minus"></i></a>';
-          template += '<a class="panel-menu-icon pull-left" ng-click="ctrl.updateColumnSpan(1)"><i class="fa fa-plus"></i></a>';
+          if (!ctrl.dashboard.meta.fullscreen) {
+            template += '<a class="panel-menu-icon pull-left" ng-click="ctrl.updateColumnSpan(-1)"><i class="fa fa-minus"></i></a>';
+            template += '<a class="panel-menu-icon pull-left" ng-click="ctrl.updateColumnSpan(1)"><i class="fa fa-plus"></i></a>';
+          }
           template += '<a class="panel-menu-icon pull-right" ng-click="ctrl.removePanel()"><i class="fa fa-trash"></i></a>';
           template += '<div class="clearfix"></div>';
           template += '</div>';