-added landing page and module page -linked to Qt Multimedia and Qt Widgets -excluded multimediawidgets dir from the Qt Multimedia documentation Task-number: QTBUG-29339 Change-Id: Iaa8dc4117505d5635b8cab97ed5c10e9c4a289e6 Reviewed-by: Lars Knoll <lars.knoll@digia.com> Reviewed-by: Sze Howe Koh <szehowe.koh@gmail.com>