Added user email modification to admin page

Pressing the user settings button brings up a list of all jellyfin
users, and allows you to add or change their stored email addresses.
Additionally, changed emails.json to use user ID instead of username.
The program automatically converts the file to the new format at start.

jellyfin_accounts/pw_reset.py

@@ -3,6 +3,7 @@ import json
 from watchdog.observers import Observer
 from watchdog.events import FileSystemEventHandler
 from jellyfin_accounts.email import Mailgun, Smtp
+from jellyfin_accounts.web_api import jf
 from __main__ import config
 from __main__ import email_log as log
 
@@ -41,7 +42,8 @@ class Handler(FileSystemEventHandler):
                 try:
                     with open(config['files']['emails'], 'r') as f:
                         emails = json.load(f)
-                        address = emails[reset['UserName']]
+                        id = jf.getUsers(reset['UserName'], public=False)['Id']
+                        address = emails[id]
                     method = config['email']['method']
                     if method == 'mailgun':
                         email = Mailgun(address)