Add support for microsite overrides (template & configuration) for the ID Verification Status display on the dashboard

Please note that this is a squshed commit and the work of:
Symbolist, macdiesel, nedbat, doctoryes, muzaffaryousaf and muhammad-ammar

ECOM-2547

Also remove useless docstrings where they were added to keep pylint
quiet.

ECOM-2552

add new column 'copy_id_photo_from' for 'SoftwareSecurePhotoVerification' model to track initial verification with 'photo_id_key'

* Automatically create user partitions on course publish for each ICRV checkpoint.
* Disable partitions for ICRV checkpoints that have been deleted.
* Skip partitions that have been disabled when checking access.
* Add verification access control UI to visibility settings.
* Add verification access control UI to sequential and vertical settings.
* Add partition scheme for verification partition groups.
* Cache information used by verification partition scheme and invalidate the cache on update.
* Add location parameter to UserPartition so the partition scheme can find the associated checkpoint.
* Refactor GroupConfiguration to allow multiple user partitions.
* Add special messaging to ICRV for students in the honor track.

Authors: Zubair Arbi, Awais Qureshi, Aamir Khan, Will Daly

* Combine verification and reverification photo submission end-points.
* Combine verification and reverification Backbone models.
* Allow deletion of verification status in Django admin.
* Initial verification from a checkpoint is associated with the checkpoint.
* Fix critical bug in which an invalid link was sent to Software Secure
  for the photo ID image of reverification attempts.

* Add verification deadline model.
* Populate verification deadlines from course modes table.
* Update student dashboard to use verification deadlines.
* Update pay-and-verify view to use verification deadlines.
* Simplify Django admin for course modes and add validation.
* Add verification deadline to Django admin for course modes.
* Add UI for when the upgrade deadline is missed in the pay-and-verify flow.

ECOM-1612

* Ensure that VerificationStatus is append-only and immutable.
* Allow searching by student for verification status.
* Properly pluralize verification status.
* Use ConfigModelAdmin for ICRV config model admin.

TNL-1886

ECOM-1477

ECOM-1228

due to expiration.

LMS-2192