Various minor Audit UI improvements

Summary:

• Order audits by id desc so they tend to be in descending time order, like other content.
• In audit tables without commit context (audit tool, home page) show commit descriptions.
• Correctly hide pagers on "active" audit filter.
• Make pagers work correctly on commit / audit views.

Test Plan: Looked at homepage, audit, owners, differential. Paginated relevant interfaces.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran, epriestley

Maniphest Tasks: T904

Differential Revision: https://secure.phabricator.com/D1875