File name corrections for Stargate artifacts

This is a follow on issue to: #383 (closed)

The latest files built from the Stargate pipeline stage have been reviewed and need some modifications. Specifically, two modifications are needed:

1) All base file names must match

The external metadata file name and corresponding signature file must match the base file name of the package and package signature file.

The latest files from the pipeline have mismatched names:

In the vault example, the four file names should be:

1. vault.tar.gz
2. vault.tar.gz.sig
3. vault.metadata
4. vault.metadata.sig

or

1. vault-1441.tar.gz
2. vault-1441.tar.gz.sig
3. vault-1441.metadata
4. vault-1441.metadata.sig

vault.tar.gz.sig should be uploaded last as that tells our Lambda function to check for the presence of the other three files.

The "base file name" (vault or vault-1441 in this case) does not matter as long as the filenames are valid S3 URIs. I would recommend making it something useful for clearly identifying packages with an S3 listing versus requiring inspection of the file contents. For instance, you may want to have differing file names based on tag (version) and the docker project path.

2) Metadata file within package should be named metadata.json

The metadata file within the package should always be named metadata.json vs. the same name as the external metadata file (e.g., vault.metadata).