dashboard: add Import button to manage page

public/app/core/components/manage_dashboards/manage_dashboards.html

@@ -13,6 +13,10 @@
       <i class="fa fa-plus"></i>
       Folder
     </a>
+    <a class="btn btn-success" href="{{ctrl.importDashboardUrl()}}" ng-if="ctrl.hasEditPermissionInFolders || ctrl.canSave">
+      <i class="fa fa-plus"></i>
+      Import
+    </a>
   </div>
 
   <div class="page-action-bar page-action-bar--narrow" ng-show="ctrl.hasFilters">

public/app/core/components/manage_dashboards/manage_dashboards.ts

@@ -294,6 +294,16 @@ export class ManageDashboardsCtrl {
 
     return url;
   }
+
+  importDashboardUrl() {
+    let url = 'dashboard/import';
+
+    if (this.folderId) {
+      url += `?folderId=${this.folderId}`;
+    }
+
+    return url;
+  }
 }
 
 export function manageDashboardsDirective() {