Allows the admin to register a new member through the admin center.

• Accessed at index.php?action=regcenter;sa=register
• Allows the admin to choose various options such as membergroup, whether or not to require account activation and whether or not to email a random password to the user
• Due to a bug in 1.0.x, this didn't work if you weren't an admin (register2 didn't check for moderate_forum permission in a couple of spots)