Accept an artifact file as input

Currently, to analyze an artifact we accept a Package URL (PURL) or repository path as input. We also need to accept the artifact file itself as input if available.

Note that artifacts should be supported with [the current data model ](https://oracle.github.io/macaron/pages/developers_guide/apidoc/macaron.database.html#module-macaron.database.table_definitions)in mind.