Add unique user id (not actual id) to cookie names.

[simjanos-dev]

Most settings are saved to cookies, but if there will be multiple users on one device in the future, they may prefer different settings, so the cookies should be separated per user.

Cookie values do not contain private data, only settings. But it is better to use to hash made from user id + name together, so the actual user id won't be stored in the cookie names.