Preference dialog split into two dialogs.
Both the two new dialogs and the old one are active and working at the same time. The old one will be removed when everything is in place.
New preference icons are added for classical theme.
Placeholder icons added for all monochrome themes.
The only thing not moved is the splash screen functionality. It does not really fit in either dialog and there are allready another special dialog for customizing splash screens. Perhaps make a combined dialog for all splash screen work? Will think about it tomorrow.