Add hint for empty lists (device properties, contacts, attachments, customfields)

When I look at a new created device, most of the lists in the various tabs are empty. As there is nothing to see (unless the user enters edit mode), it would be useful to have a hint here similar to the one in the actions tab:

Affected are:

• contacts (usually there is at least one contact for the newly created device, but I can remove this one, and than there is nothing as well)
• measured quantities
• custom fields
• attachments

The same is true for those tabs on platforms, and the contacts tab of the configurations. Also the platform-and-devices tab of the configurations has no hint if there is no mounted platform/device for the selected date.