bring in classes to support conversation view's subject/labels

No functional change.

Bring in classes and refactor existing folder-display related
classes. Remove FolderValues and use plain Folder. If we need
somewhere to tuck display-only Folder properties or behavior, we
should wrap base Folders instead of duplicating fields.

Folder objects now support equality checking using the
(globally unique) URI.

Change-Id: Ic4cd9b555a6a71ed037a1e730f36f7f64c50ca36
11 files changed