#15 user table can end up with dups

[Michael Nash]

There is no unique key being created on the login name in the
keelusers table with this module. Running createdb multiple times
can result in multiple users called "root", all with different UID's -
none of which are authorized to do anything. Net result: you log in
as root and don't have permission to do anything.

Need a way to assign a uniqe index (not the primary key).
Also, when creating default records for this table, force the
primary key to the fixed values for special users such as root,
anonymous and guest.