Introduced changes to support the multi-tenant backend architecture

As announced, commercetools Frontend now has a multi-tenant backend architecture. The Studio underwent the following changes to support the new architecture:

• Sandboxes is no longer available in the Developer area.
• From Deployment in the Developer area, you can now deploy the frontend and backend of your website at the same time.
• Using the Project schema and the Project area, you can now manage additional project configurations, such as API credentials.

Our documentation is updated to reflect the changes.