Embedded cover art support

[Nikolaj Hald Nielsen]

> Just for the fun of it and to familiarize myself with Amarok code I tried a
> much simpler approach which leaves the database layout untouched and more or
> less just accepts a music file with an embedded APIC frame as a valid entry in
> the image table which is used whenever no other cover-art image file is found.
> With just some minor modifications to the image loading process the result
> works for me as expected.

I'm not an expert on the database scheme, but I think this sounds like
an excellent way of solving this issue as it minimizes the amout of
code that needs changing and thus the risk of serious regressions
creeping in.

Good thinking! :-)

- Nikolaj