Reverse project paging order

Summary:
Currently, we're showing projets in reverse order (Z..A) because most cursor pagers go from high IDs to low IDs.

Allow sequence to be reversed; reverse it.

Also simplify some query/paging stuff.

Test Plan: Set page size to 1, paged back and forth.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Maniphest Tasks: T603

Differential Revision: https://secure.phabricator.com/D3221