Remove getPagingColumn() / getReversePaging()
Summary: Ref T7803. Remove these in favor of more generalized paging and ordering.
Test Plan: Sorted and paged results in various applications.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T7803
Differential Revision: https://secure.phabricator.com/D12378