PLT-1866/PLT-3509 Added links to download the native apps (#3651)

* PLT-1866 Added configurable links for native app downloads

* PLT-1866 Added native app download link to main menu

* PLT-3509 Added native app link to tutorial

* PLT-3509 Added native app link to welcome email

* PLT-3509 Made link to apps in welcome email conditional on being set

templates/welcome_body.html

@@ -33,6 +33,17 @@
                                                 <p>{{.Props.Info3}}</p>
                                             </td>
                                         </tr>
+                                        {{if .Props.AppDownloadLink}}
+                                        <tr>
+                                            <td style="border-bottom: 1px solid #ddd; padding: 0 0 20px;">
+                                                <p>{{.Props.AppDownloadInfo}}</p>
+                                                <a href="{{.Props.AppDownloadLink}}">
+                                                    <p>{{.Props.AppDownloadLink}}</p>
+                                                    <img src="{{.Props.SiteURL}}/static/images/appIcons.png" />
+                                                </a>
+                                            </td>
+                                        </tr>
+                                        {{end}}
                                     </table>
                                 </td>
                             </tr>