Merge behavior-show-more into behavior-populate
Summary: Ref T2009. It doesn't make sense to have these as separate behaviors. We require a ChangesetViewManager to track view parameter state.
Test Plan: Interacted with changesets in Phriction, Differential and Diffusion.
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T2009
Differential Revision: https://secure.phabricator.com/D11979