Adding an option to show popular documents/apps for Kicker and Dash

Summary:
Kicker:
{F3601847}

Dash:
{F3601849}

Settings:
{F3601850}
{F3601851}

Reviewers: mart, hein

Reviewed By: hein

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D5378