Swagger UI: add support for OAuth2 authentication

[avas]

Problem:
Currently, Swagger UI relies on cookie-based authentication. But, as of #1476, the VirtoCommerce platform won't be using cookies for authentication anymore - it uses OAuth2 Password Grant Flow instead. It is not supported by the swagger-ui.js used in the platform, so the authentication fails for methods that require additional authorization, e.g. GET /api/platform/security/user/{userName}:

Solution:
The easiest solution would probably be to update the swagger-ui. Current version (3.20.1 at the moment of writing this) has built-in support for OAuth authentication:

Proposal of changes:

• Install updated version of swagger-ui (from bower or directly from the swagger-ui repository);
• Update the SwaggerConfig.cs to include it's files;
• Apply VirtoCommerce branding to it;
• Apply tags auto-collapsing;
• Investigate what else had been changed in swagger-ui.js for VC Platform. If there were some valuable changes, they need to be applied too.

[dvs39]

[tatarincev]

Released https://github.com/VirtoCommerce/vc-platform/releases/tag/v2.13.39