add "weed copy" command to copy files to filer

weed/server/filer_server_handlers_admin.go

@@ -27,3 +27,15 @@ func (fs *FilerServer) moveHandler(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
 	}
 }
+
+func (fs *FilerServer) registerHandler(w http.ResponseWriter, r *http.Request) {
+	path := r.FormValue("path")
+	fileId := r.FormValue("fileId")
+	err := fs.filer.CreateFile(path, fileId)
+	if err != nil {
+		glog.V(4).Infof("register %s to %s error: %v", fileId, path, err)
+		writeJsonError(w, r, http.StatusInternalServerError, err)
+	} else {
+		w.WriteHeader(http.StatusOK)
+	}
+}