Add constants for app features

src/components/multiSelect/multiSelect.js

@@ -1,3 +1,4 @@
+import { AppFeature } from 'constants/appFeature';
 import browser from '../../scripts/browser';
 import { appHost } from '../apphost';
 import loading from '../loading/loading';
@@ -198,7 +199,7 @@ function showMenuForSelectedItems(e) {
                 });
             }
 
-            if (user.Policy.EnableContentDownloading && appHost.supports('filedownload')) {
+            if (user.Policy.EnableContentDownloading && appHost.supports(AppFeature.FileDownload)) {
                 // Disabled because there is no callback for this item
             }