And then use this to add the "Open in Graphical Shell" and "Open in
Terminal" actions.

Those actions cannot be implemented in Utils directly since the Core::FileUtils
depends on the Options dialog.

This affects all PathChoosers, and there's currently no way for a PathChooser
to opt out or have a different context menu. That can be added at a later
point.

Change-Id: I22121c19d66f08785381c7e0bca5317628eb6342
Task-number: QTCREATORBUG-14736
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>