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/sqlstore/dashboard.go

@@ -266,6 +266,7 @@ func makeQueryResult(query *search.FindPersistedDashboardsQuery, res []Dashboard
 			}
 			hit = &search.Hit{
 				Id:          item.Id,
+				Uid:         item.Uid,
 				Title:       item.Title,
 				Uri:         "db/" + item.Slug,
 				Url:         url,