folders: change the front end route for browsing folders

Change the front end route for folders to /dashboards/f/<uid>/<slug of folder title>.
Use new route for deleting dashboard/folder by uid.
Retrieve dashboard/folder by uid when moving or deleting dashboards/folders.

pkg/services/search/models.go

@@ -13,6 +13,7 @@ const (
 
 type Hit struct {
 	Id          int64    `json:"id"`
+	Uid         string   `json:"uid"`
 	Title       string   `json:"title"`
 	Uri         string   `json:"uri"`
 	Url         string   `json:"url"`