Importer should be able to import vulns and packages

[TG1999]

          A future step will be to inline all this so import is called one at a time right after each call here https://github.com/nexB/vulnerablecode/pull/1280/files#diff-11856d929972b1aa71dcd476298a831d6b598b291c0638057af6d62050ba4a15R92

Originally posted by @pombredanne in #1280 (comment)