Version 2.3.1 (r3198) (20060705)
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The user database structure is changed. Now the majority of
user info fields are contest-specific. For example, the `name'
field (the user name) may be different for the same user (more
precisely, for the same login) in different contests. In the
previous versions all the user information fields are
contest-independent, so change of the `name' field for one
contest automatically changed the `name' of the user in all
other contests, even had finished long ago.

For backward compatibility with the accumulated user database
the existing information about users are considered as specific
to the special "default contest" (which has the indentifier as
0). This information is used, when no contest-specific
information is available for a particular contest. However, as
soon as an existing user (or an administrator) changes
information about the user in the contest, a copy of user
information fields is created and made contest-specific for this
contest, so only the data for the contest is changed, but the
default data is left intact.

Only `login', `e_mail' and `password' user-settable fields are
contest-independent. All other user-editable fields are
contest-specific.

The `read_only' field now means that the user information
cannot be changed for any contest, except the registration
password, which can still be changed.

A new `cnts_read_only' field is added, which means that the user
information cannot be changed by the user for the particular
contest, but the team password can still be changed.