Generate expected schemata for Doorkeeper, Draft, Drydock, Feed

Summary:
Ref T1191. Notable:

  - Allowed objects to remove default columns (some feed tables have no `id`).
  - Added a "note" severity and moved all the charset stuff down to that to make progress more clear.

Test Plan:
Trying to make the whole thing blue...

{F205970}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10519