- This removes the duplication across the various IDA configurations
- Updated Dockerfile for Docker-based devstack

LEARNER-817

`DATABASE_OPTIONS` was deprecated in Django 1.2 and removed in 1.4.
`OPTIONS` should now be passed as part of `DATABASES`.

This should have been set prior to https://github.com/edx/auth-backends/pull/9 being merged. We did not catch this problem until now because the library currently used for JWT validation, pyjwt, simply skips issuer validation if the issuer is set to None.

LEARNER-693

ECOM-7207

ECOM-5776

These defaults are conflicting with the overrides.

ECOM-6238

ECOM-6141

Update the configuration for the non-ses email backends.

ECOM-5847

ECOM-5134

ECOM-5173

ECOM-4786

ECOM-4678

ECOM-4609

The JWT configuration for IDAs that depend on edxapp's JWT configuration have been updated to actually reference the edxapp variables.

ECOM-4414

python-memcached seems to have sporadic issues with Python 3.5.

ECOM-4370

ECOM-4368

Using EDXAPP_LMS_ROOT_URL instead of EDXAPP_LMS_ISSUER. This removes the need to define another EDXAPP_* override in our secure variables.

ECOM-3602

The EDXAPP_LMS_ROOT_URL has been added to simplify the addition of LMS-hosted URLs to IDA configurations.

ECOM-3602

The headers were pointing to the old github wiki. Since we've officially
moved to Confluence, these links should be updated.

ECOM-3895

ECOM-3895

This has caused confusion in the past. Updated the value to actually be the OAuth2 endpoint, rather than the LMS host.

ECOM-3895

N.B. This may break docker-based devstacks. Fix TBD.