Added missing icons to panel places items

Summary:
Screenshots of the changes:
| {F6310217} |{F6310218}

This contribution was motivated by a comment on [[ https://pointieststick.wordpress.com/2018/10/06/this-week-in-usability-productivity-part-39/comment-page-1/#comment-2108 |  Nate's blog]].

Reviewers: #vdg, ngraham

Reviewed By: #vdg, ngraham

Subscribers: ngraham, acrouthamel, kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D16019