Show a more reasonable status element for pull requests
Ref T182. Replace the total mess we had before with a sort-of-reasonable element.
Used "Land Revision", saw the land status go from "Waiting" -> "Working" -> "Landed" without having to mash reload over and over again.
Reviewed By: chad
Maniphest Tasks: T182
Differential Revision: https://secure.phabricator.com/D14314