Adjust KWin defaults

Reasoning for the change:
http://userbase.kde.org/Desktop_Effects_Performance#Qt_Graphics_System

Last touches for the plasma-theme:
Added: phone, lazy eyes and activities icons
Improved contrast for widget icons
Adjust Lancelot background for modern times
Fixed scrollbar as per bnc#803437
Slighty tweak dialog/panel svg, so notifications don't get cut off (mostly noticeable when new mail arrives in multiple folders)