Support AUTO_INCREMENT in `bin/storage adjust`

Summary:
Ref T1191. When changing the column type of an AUTO_INCREMENT column, we currently may lose the autoincrement attribute.

Instead, support it. This is a bit messy because AUTO_INCREMENT columns interact with PRIMARY KEY columns (tables may only have one AUTO_INCREMENT column, and it must be a primary key). We need to migrate in more phases to avoid this issue.

Introduce new `auto` and `auto64` types to represent autoincrement IDs.

Test Plan:
  - Saw autoincrement show up correctly in web UI.
  - Fixed an autoincrement issue on the XHProf storage table with `bin/storage adjust` safely.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T1191

Differential Revision: https://secure.phabricator.com/D10607