Improve usage metrics logging and replace Alias API view functions with ModelViewSet subclass

[manning-ncsa]

Resolves #473

Changed

• Improved the usage metrics logging system to handle class-based views, including the individual Blast data object endpoints and the transient dataset download endpoints.
• Replaced Alias API view functions with ModelViewSet subclass for consistency with other data object API endpoints and to benefit from the Django REST Framework. (While this API change is technically not backwards-compatible, the nature of the /api/alias/ functionality and its lack of known use to date justifies this "minor" violation of semantic versioning.)