QmlDesigner.TabViewContextMenu: Remove direct dependencies

The code for creating new files and addFileToVersionControl can be moved
to the DocumentManager.

Change-Id: I222a32f245da24d7308289a9bb6d30574da55387
Reviewed-by: Marco Bubke <marco.bubke@digia.com>
QmlDesigner: Move TabViewDesignerAction to componentsplugin

Change-Id: Ib02092d38d4ba43ad3bed2460f7eb9615bd06fa7
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>