KFilePlacesModel: On new profile in recent show only recentlyused:/ based entries by default

Summary:
The places timeline:/today and timeline:/yesterday are way less useful than recentlyused:/files and recentlyused/folders.
We should expose only one of the two for new installations, to not clutter UI.

Test Plan:
rm ~/.local/share/user-places.xbel

Before:

After:

Reviewers: ngraham, VDG, Plasma, hein

Reviewed By: ngraham, VDG

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D26782