Improve Kickoff touch interaction and general aesthetics

Improve Kickoff touch interaction by increasing list items and footer items vertical padding. Also de-clutter Kickoff by removing header and footer vertical lines which aren't needed because there's a clear distinction between elements.

These changes made using Kickoff with a touch screen much easier than before without dramatically changing the appearance.

The before:

The after:

PD: Since I'm not familiar with the coding style used in KDE, please forgive me if I wrote something terribly wrong