Add a bin/auth revoke revoker for SSH keys

Summary: Ref T13043. Adds CLI support for revoking SSH keys. Also retargets UI language from "Deactivate" to "Revoke" to make it more clear that this is a one-way operation. This operation is already correctly implemented as a "Revoke" operation.

Test Plan: Used bin/auth revoke --type ssh to revoke keys, verified they became revoked (with proper transactions) in the UI. Revoked keys from the web UI flow.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13043

Differential Revision: https://secure.phabricator.com/D18893