Each account has an associated weak account key.
The user can see it by visiting weak_auth.php.
If you put the weak account key in the account file on a computer
(instead of the regular account key)
the computer will attach to the account.
But the weak account key cannot be used to log in
to the account on the web, or to do web RPCs, or anything else.
Note: this involves a scheduler change.
svn path=/trunk/boinc/; revision=14367
