Add email-to option in action buttons for dashboard and slice (#1705)

* Add email-to option in explore action buttons

* email to option for dashboard

superset/assets/javascripts/dashboard/components/Controls.jsx

@@ -44,6 +44,9 @@ class Controls extends React.PureComponent {
   render() {
     const dashboard = this.props.dashboard;
     const canSave = dashboard.context.dash_save_perm;
+    const emailBody = `Checkout this dashboard: ${window.location.href}`;
+    const emailLink = 'mailto:?Subject=Superset%20Dashboard%20'
+      + `${dashboard.dashboard_title}&Body=${emailBody}`;
     return (
       <ButtonGroup>
         <Button
@@ -93,6 +96,11 @@ class Controls extends React.PureComponent {
             <i className="fa fa-save" />
           }
         />
+        <Button
+          onClick={() => { window.location = emailLink; }}
+        >
+          <i className="fa fa-envelope"></i>
+        </Button>
       </ButtonGroup>
     );
   }