Generate expected schemata for Dashboards and Conpherence

Summary:
Ref T1191.

  - Add edge schemata generation.
  - Hit a couple of mostly-minor issues (T6128, T6129, T6130).

Test Plan: Viewed schema in web UI.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10518