[Image Wallpaper] Add "Open Containing Folder" button

Authored by broulik on Jun 30 2017, 1:10 PM.

Description

[Image Wallpaper] Add "Open Containing Folder" button

This allows to open the location of the folder the wallpaper is in.

BUG: 371247
FIXED-IN: 5.11.0

Differential Revision: https://phabricator.kde.org/D6450