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