Ground Versions Save

• Add API to retrieve the latest version(s) of an Item.
• Add API to retrieve the history of an Item.
• Add API that retrieves lineage edge versions adjacent to a particular node version.

• Fixed bug that prevented the creation of lineage graphs.
• Fixed null serialization issue for some strings.
• Removed required empty data structures (i.e., the user no longer has to provide an empty tags map if no tags are being added).

Initial release for Ground. The Ground server is Play app that provides REST APIs to interact with the Ground metamodel.

The initial release of Ground supports only Postgres as a storage backend. See our getting started guide for more information on configuring and using Ground.