Create new API endpoint to return all relationships for all artifacts at once.

[hack-sentinel]

Create new API endpoint to return all of the relationships for all of the artifacts at once, in one file.

At present, to assemble all the relationships in one .json file requires making N requests (one for each artifact) against the d3fend/api/dao/artifact path. That is, the user has to import each one, find rel data, and then process it.

-[ ] Will need to consult with requestor to make sure file contains what is expected and use of data in file (or drawn from files, currently)