Log which users were migrated

[nickrod518]

Save the users that were migrated to a text file within the migration store. This may not be possible when using the option to migrate all users that have logged in within a certain time, but it should be possible in all other cases. This should help during the load state to deal with checking for cross domain migrations when multiple users were selected. It may also be useful so that someone can view the save state migration store and see at a glance what profiles it contains.