Rename "PhabricatorPasswordHashInterface" to "PhabricatorAuthPasswordHashInterface"
Summary: Depends on D18911. Ref T13043. Improves consistency with other "PhabricatorAuthPassword..." classes.
Test Plan: Unit tests, grep.
Reviewers: amckinley
Reviewed By: amckinley
Maniphest Tasks: T13043
Differential Revision: https://secure.phabricator.com/D18916