Generate expected schemata for User/People tables

Summary:
Ref T1191. Some notes here:

  - Drops the old LDAP and OAuth info tables. These were migrated to the ExternalAccount table a very long time ago.
  - Separates surplus/missing keys from other types of surplus/missing things. In the long run, my plan is to have only two notice levels:
    - Error: something we can't fix (missing database, table, or column; overlong key).
    - Warning: something we can fix (surplus anything, missing key, bad column type, bad key columns, bad uniqueness, bad collation or charset).
    - For now, retaining three levels is helpful in generating all the expected scheamta.

Test Plan:
  - Saw ~200 issues resolve, leaving ~1,300.
  - Grepped for removed tables.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10580