CLC-4108 - Add logger statements to assist in migration to preferred name use

https://jira.ets.berkeley.edu/jira/browse/CLC-4108

* Adds logger statements to assist in migration to preferred name use
* Adds option to update users with 'clear_sis_stickiness' mode enabled
… and unneeded, since SisImport's import_users method defaults the argument to ''.