Kicker/RecentDocument display file path as decoration

Summary: Also add an open containing folder action

Test Plan: {F7828041}

Reviewers: #vdg, #plasma, ngraham, ervin, hein

Reviewed By: #vdg, #plasma, ngraham, ervin, hein

Subscribers: davidre, broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D26121