Implement initial Azure Media Service REST API communication

[oksana-slu]

@kabirkhan @saravpal

1. Extended native OpenEdx Organization model with SettingsAzureOrganization model;
2. Configured admin section for SettingsAzureOrganization model fields;
3. Created client to communicate with Azure Media Service API - MediaServicesManagementClient;
4. Implemented xBlock studio view to customize editing modal window behavior;
5. Switched from Mako to Django template engine;
6. Configured initial CircleCI service automatic checks;
7. New code base covered with unit tests.

AMS content is shared per OpenEdx organization

Technically AMS API credentials are configured per Organization. If there is no explicit configuration for the current organization - fallback to global (per OpenEdx installation) configuration is performed. To configure global AMS API ones should add to lms.env.json into FEATURES section following settings:

"AZURE_CLIENT_ID": <azure-open-directory-app-id>
"AZURE_CLIENT_SECRET": <azure-open-directory-app-secret-key>
"AZURE_TENANT": <azure-open-directory-id>
"AZURE_REST_API_ENDPOINT": <azure-media-service-rest-api-endpoint>

CircleCI service automatic checks include:

• python code style (flake8);
• javascript code style (eslint);
• python unit tests (nose, coverage);
• javascript unit tests (karma, jasmine).

To be able to run all checks manually ones should:

NOTE: assuming Ubuntu as a testing environment OS

• create and activate new python virtualenv;
• change dir to project's root;
• install base system dependencies packages:

  make install-tools

• install project dependencies:

  make install-dev

• install testing dependencies:

  make install-test

  After that, it is possible to run project checks:

  # run all together:
  make all
  # run unit tests only:
  make test
  # run code style (quality) checks only:
  make quality
  # help:
  make help

[msftclas]

All CLA requirements met.

[sdolenc]

I apologize it has taken me so long to review this. The PR was submitted while I was out on vacation so I missed it, but I should have time to review it this afternoon update:

• I will not have time to finish reviewing this today, but I should be able to complete the review tomorrow. I'm impressed with the parts I've seen thus far and look forward to seeing the rest of it. Great work!
• I've also added @kabirkhan to the review in case he has the chance to take a look as well.

[kabirkhan]

Awesome initial work!