ECOM-4217

ECOM-4217

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.

The old line:

    from path import path

produced pylint errors because of the baroque way that path.py defined
"path".  We tried to get them to change how they defined it, but they
deleted the name instead: https://github.com/jaraco/path.py/issues/102

(Jason then changed his mind, but this is a better way to use path.py,
it avoids the pylint error at least.)

* removing visual-based heading styles from 'sr-only' DOM elements
* revising default certificate view h1/heading copy
* revising DOM elements to use main/aside semantics
* revised edX/platform logo link alt text
* removed extra share/take home header text
* synced up add to LinkedIn profile copy

Add the ability to generate "example" certificates to
test that certificate generation is working correctly for a course.

Add the ability to enable/disable self-generated certificates
on a per-course basis.