feat: several improvements to azlux's token auth scheme #154

1. 'auth_method' in config, where users can select between
   'password' and 'token'.
2. create index for token, avoid iterating the entire user
   section when validating tokens.
3. only generate token for a user when there's no token for
   him in the db, avoid tokens fill the db.

static/js/custom.js

@@ -928,6 +928,7 @@ function uploadNextFile(){
     form.append('targetdir', uploadTargetDir.value);
 
     req.open('POST', 'upload');
+    req.withCredentials = true;
     req.send(form);
 
     file_progress_item.progress.classList.add("progress-bar-striped");