No icons on the desktop by default

Summary:
Don't add Home.desktop to links folder and don't add trash link.

Closes T7948

Test Plan: Start plasma as new user

Reviewers: Plasma, hein

Reviewed By: Plasma, hein

Subscribers: ngraham, broulik, hein, mart, zzag, plasma-devel

Tags: Plasma

Maniphest Tasks: T7948

Differential Revision: https://phabricator.kde.org/D10588