Sheepdog-exporter

Mostly removes code and adds better usage instructions by using upstream features (3).

The manifest entry in the output JSON has been renamed to `data_objects` to make its contents more clear.

Known Issues:
* sheepdog-exporter does not have a "quiet mode" 12
* `_all` and `root` metadata types do not serialize to JSON properly 8

Exports data from sheepdog and finds the paths from indexd. The resulting manifest is written as a list of Data Objects.

The attached topmed-public.json *does not *include manifest entries for the CRAM index files.

Export metadata from the DCP!


sheepdog-exporter program project

sheepdog-exporter program project --dcp-url my-url --credentials path/to/credentials --output-path /path/to/write/output


This will write a `.json` file with the corresponding metadata
with a filename corresponding to the program and project. `program-project.json`.