Review Request: Add fade effect to wallpaper plugin.

[Dominik Haumann]

[...]
> > Also the PictureFrame plasmoid comes to my mind here. A fade effect
> > would be very nice as well and is the same code. Can it be shared
> > somehow?
>
> this sort of thing really belongs in Animator or its successor; this
> needs to become a set of standardized effects that we can implement
> internally for consistency. it would use kinetic internally, but
> shouldn't expose that detail directly.

Ah of course. I wonder why I didn't think about this myself in the first 
place ;) This definitely sounds like the right way (tm).

> that means we need a list of effects that we would like. fade is one,
> spin would be another. let's start making a list; i've added
> workspace/plasma/design/standardEffects to svn for that purpose.

@Crossfade effect: maybe also the type of the easein/out, but that's 
probably already included in the "timeelapse" parameter.

Cheers,
Dominik