Load all keys, support unique keys, and provide an "all issues" view

Summary:
Ref T1191. Three parts:

• The old way of getting key information only got primary / unique / foreign keys, not all keys. Use SHOW INDEXES to get all keys instead.
• Track key uniqueness and raise warnings about it.
• Add a new "all issues" view to show an expanded, flat view of all issues. This is just an easier way to get a list so you don't have to dig around in the hierarchical view.

Test Plan:

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10525