CSV Import Add Subscribers

I understand that the default behaviour when importing ideas via CSV is not to add that user as a subscriber, however it should be possible to override this on import.

One solution would be to add a "Subscribers" column on the import template, allowing admins to add the email address of the creator or other users if they wished.  The default behaviour could them be maintained, but overridden as desired.

The list should be comma separated to allow for the definition of multiple subscibers