Feature/empty project

[bwalsh]

This PR:

• adds feature empty_project: removes all metadata for graph from project

This PR is paired with:

• https://github.com/ACED-IDP/aced_etl_pod/pull/25
• https://github.com/ACED-IDP/submission/pull/17
• https://github.com/ACED-IDP/gen3_util/pull/53

[bwalsh]

@matthewpeterkort: changes to fhir_store look good. I have some pytests, that I will check into the next branch