Gitea user and organization feed token scope bypass

The `/{username}` web route accepted personal access tokens over HTTP Basic authentication without checking their scope. A token confined to an unrelated scope, such as `read:issue`, could read its owner's private activity through the user RSS/Atom feed and the profile activity tab, and other members' activity in a private organization through the organization feed; a public-only token could list the owner's private repositories and organizations and render private profile READMEs. For a site administrator's token this applied to every account. Tokens are now accepted on this route only for feeds, which require `read:user` or `read:organization`.