Ability to see who has registered and accessed the member interface

[tbar0970]

Pastors and administrators like to know who is using the members interface.

Several ways to achieve this:
1a) A read-only field when viewing an individual person: "Is registered for members interface"
1b) A read-only field when viewing an individual person: "Last login to members interface"
2a) A page listing all the member accounts that have been registered
2b) A page listing all the mmeber accounts and when they were last used.

[GatesheadBen]

This feature could be implemented for both User login and Member login.
I have been experimenting with this on the User side in test by

1. Adding a table called login_log with 2 columns user and timestamp
2. Adding a line to user_system.class.php like
   $loginlog = $GLOBALS['db']->query('insert into login_log set user='.(int)$_SESSION['user']);
3. Adding a new page which exposes that login_log to admins
4. Adding a column to the Users table showing last login