Remove IconLoader (i.e. Amarok's icon mapping). We are now using the spec defined fallback system (hence use a -amarok suffix for all new icons, in case we have to ship them with our source to prevent a raise of the KDE dependency). Ready to go Oxygen now :-D

I'll check for wrong converted icons (shouldn't be any from looking at the diff) and create a list of icons we need. IconLoader.cpp sticks around for now, since it is a fairly complete list of used icons.