Implement DELETE admin tasks for tags and submissions

[lewismc]

The OpenAPI spec should be extended to permit

• DELETE /tags - delete all tags, submissions and events
• DELETE /tags/{tag_id} - delete an individual tag, all associated submissions and events
• DELETE /tags/{tag_id}/subs/{sub_id} - delete an individual submission and associated events

Eventually once we implement events we can expand to the following...

• DELETE /events - delete all events for all tags and submissions
• DELETE /events/{event_id} - delete an individual event

[lewismc]

This should most likely be implemented after tagbase has been secured e.g. #27

[vtsontos]

I would recommend creating a stored procedure in tagbase that would cycle through and delete records for a specified Tag_ID. This procedure then could either be invoked by the Tagbase DBA in postgres itself or via an API call that would be implemented leveraging that stored procedure. I think this approach generally provides greater flexibility and allows quicker implementation and testing.

[lewismc]

Sample REST API design at https://github.com/tagbase/tagbase-server/pull/228