the CLI and Stores should be able to query for null/non-null elements #49
Description
A common idiom is to want to see what objects in a store have/have not been set (are not null and null resp). For instance, in OA4MP, a transaction that has a no access token might be in an abandoned flow. Rather than have to resort to firing up the command line SQL client, just have a Store call that does it and expose that in the CLI.