resolve issue 1537: improve widgets in Properties dialog
Create a symbolic link with a very long path, pointing to a long path, and then examine it in the Properties dialog. Existing 'Link Target' and 'Location' property value widgets cause long canonical paths to be cut off, preventing the ability to focus the widget, select-all, and copy-to-clipboard. Relevant widgets were changed to frameless, read-only GtkEntry widgets to allow "copy canonical path to clipboard", using mouse or keyboard with equal ease.