Two new certificate statuses are introduced, 'audit_passing' and
'audit_notpassing'. These signal that the GeneratedCertificate is not
to be displayed as a cert to the user, and that they either passed or
did not. This allows us to retain existing grading logic, as well as
maintaining correctness in analytics and reporting.

Ineligible certificates are hidden by using the
`eligible_certificates` manager on GeneratedCertificate. Some places
in the coe (largely reporting, analytics, and management commands) use
the default `objects` manager, since they need access to all
certificates.

ECOM-3040
ECOM-3515

This reverts commit 60860e3a.

An `eligible_for_certificate` field is added to the
GeneratedCertificate model. This way we can retain existing grading
logic, as well as maintaining correctness in analytics and reporting.

Ineligible certificates are hidden by using the
`eligible_certificates` manager on GeneratedCertificate. Some places
in the coe (largely reporting, analytics, and management commands) use
the default `objects` manager, since they need access to all
certificates.

This commit also updates the DB cache for acceptance tests.

[LMS-2757]

sorted the output, easier to read

Add is_active filter to only generate for students enrolled

Adding back total_enrollment

Removing active filter

Certs will generate for all users in the course, not just those "active"

Typo

Renaming headings to make more sense

Renaming variables to match headings

This commit adds the non-courseware lms/djangoapps and lms/lib.

These keys are now objects with a limited interface, and the particular
internal representation is managed by the data storage layer (the
modulestore).

For the LMS, there should be no outward-facing changes to the system.
The keys are, for now, a change to internal representation only. For
Studio, the new serialized form of the keys is used in urls, to allow
for further migration in the future.

Co-Author: Andy Armstrong <andya@edx.org>
Co-Author: Christina Roberts <christina@edx.org>
Co-Author: David Baumgold <db@edx.org>
Co-Author: Diana Huang <dkh@edx.org>
Co-Author: Don Mitchell <dmitchell@edx.org>
Co-Author: Julia Hansbrough <julia@edx.org>
Co-Author: Nimisha Asthagiri <nasthagiri@edx.org>
Co-Author: Sarina Canelake <sarina@edx.org>

[LMS-2370]

Also removes the unnecessary pre-fetch.
For certificate generations we will continue to generate certs for
both active and inactive users.

For the report we only display active users since it was confusing
due to the instructor dashboard only displaying active users.

It doesn't make sense to print out unavailable students
since it will go negative as students unenroll

* List of courses that have ended is now a generator
* Using db-aggregation to speed up query for tallies

* Removing the command to find unicode names since it was only used for
  testing
* ungenerated_certs will now by default run through all courses that
  have ended.  a course option can be used to run on one course
* gen_cert_report added which will summarize certificate states
  for all courses that have ended