If you open a file, the path of the containing directory is preserved
as a "path" property of the data node, and the file name (without
extension) becomes the name of the node.

However, sometimes it would be useful to know the full path, including
the file extension. E.g. the node can be renamed in the data manager,
or there can be several files with the same name but different
extension.

The full path can be retrieved from the BaseData "path" property, not
from the DataNode. Hence, it is not shown in the Properties view, either.

Would it be a good idea to display the full file path in the
"Details.." dialog of the Data Manager context menu?

I attached a screenshot about how it would look. In this solution the
file path is printed by QmitkInfoDialog, but it could be done from an
appropriate place in the BaseData hierarchy as well.

A proposed implementation is pushed here:

https://github.com/NifTK/MITK/commit/84d75ed7612c5485908487a3183a7f752ca79840