Added video downloading functionality to multi user mode, as well as playlist management and saving of videos locally. Still missing video deletions and subscriptions

Simplified code for downloading videos to client (locally)

backend/subscriptions.js

@@ -9,7 +9,9 @@ var youtubedl = require('youtube-dl');
 const config_api = require('./config');
 
 const adapter = new FileSync('./appdata/db.json');
+const users_adapter = new FileSync('./appdata/users.json');
 const db = low(adapter)
+const db_users = low(users_adapter);
 
 const debugMode = process.env.YTDL_MODE === 'debug';