make sure to convert paths for displaying to native separators

Summary:
otherwise we get forwardslashes on windows, which looks silly,
in particular since the user can manually enter backslashes in the address
bar and then have the UI spit out forward ones :S

additionally retain trailing slashes, but otherwise normalize the path
to get rid of excess slashes

Reviewers: sandsmark

Subscribers: kde-utils-devel

Differential Revision: https://phabricator.kde.org/D8933