Replace context bar in Maniphest with PHUIInfoView
Summary: Removes AphrontContext bar and uses PHUIInfoView instead. This also attaches to the ObjectBox instead for cleaner UI. Also moved phui-error-view.css which was missed.
Test Plan: Test creating a subtask or a new task, see updated info bar and action buttons.
Reviewers: btrahan, epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D11920