Go through activiation even for admin accounts

Fixes an issue with accounts being locked after trying to activate it.

Addresses #330
fixing syntax error
Adding invitation system to mmcfe-ng core

This will allow users to send invitations to other people via email.
Each account will still need to confirm the email address if the option
is enabled.

Addresses #330, will need to allow pool operators to enable this feature
even with registrations turned off.