This reverts commit 793354a0.

Re-add TestCenterUser along with a basic command to make an entry for a given user already in the system.

- add a check for the feature flag before trying to save user info to the service

functionality - grade dump and download as csv, manage staff list,
force reload of course from xml

When replicating CourseEnrollment, make sure Users were created in all DBs before replicating other models

1. Multiple save()s on the same model are now handled properly. We
   had to unmark model objects after the appropriate signals had
   fired.
2. There was a side-effect where we were saving the portal User
   object to the course_db with the using kw param, but models
   remember where they were last saved to, so a later save on that
   model object would go to the wrong database.

* Changed from 'male', 'female', and 'other' to 'm', 'f', and 'o'

Added a migration with indexes on course enrollment and a unique constraint. This involves a migration that first drops the table, because there may be non-unique data there already.

* Updated student.models.UserProfile
* Added migration to add: gender, date_of_birth, mailing_address, country, telephone_number, occupation