Read-only initial version of API

This release includes some OpenAPI documentation and an initial/preliminary version of a GET, read-only API for feedback.

Features:

• GET datasets /api/datasets
• GET a dataset /api/datasets/
• GET the versions of a dataset /api/datasets//versions
• GET a version specific version /api/versions/
• GET a file information about a version /api/versions//files
• GET file information /api/files/
• Download an individual file ( /api/downloads/ ) or download other packages as shown in links
• See API documentation at /api/docs/index.html
• It includes HAL links for discovering related resoures