implement pool group and user get routes,

improvements to http return codes,
add localdb backend handler

user-manager-api.go

@@ -7,6 +7,7 @@ import (
 
 func main() {
 	configPath := flag.String("config", "config.json", "path to config.json file")
+	localDBPath := flag.String("localdb", "localdb.json", "path to localdb.json file")
 	flag.Parse()
-	app.Run(configPath)
+	app.Run(configPath, localDBPath)
 }