Add a 'Properties' entry in the Places panel context menu

Summary: BUG: 181880

Test Plan:
Right-click on a place or on a device in the Places panel now show a Properties entry.
Clicking on it will open its folder property.

Reviewers: Dolphin, Plasma, VDG, ngraham, elvisangelaccio

Reviewed By: Dolphin, VDG, ngraham, elvisangelaccio

Subscribers: anthonyfieroni, elvisangelaccio, cfeck, ngraham, abetts, kfm-devel

Tags: Dolphin

Differential Revision: https://phabricator.kde.org/D15929