[Amarok] aa4c4f5: Enable filtering by labels for the sql collections

[Nikolaj Hald Nielsen]

> The current label feature needs a complete rewrite anyway (it only
> works for SqlCollection. Labelling magnatune/ampache/media device
> track are required too imo if possible at all). I do not think adding
> a feature for which we know it is incomplete annd  will receive bug
> reports is a good idea. Does not make a very good impression  in my
> opinion. Till yesterday querying for labels was just a wishlist item
> to which we would implement eventually. Now it's a feature for which
> we did not take the time to get right.

Point taken. Reverted!

> Read http://doc.trolltech.com/4.5/qtestlib-manual.html
>
> Set KDE4_BUILD_TESTS = ON in cmake
> Set KDE4_TEST_OUTPUT = plaintext in cmake (this is the default,
> setting this to xml is only required on the CI server to make use of
> the output)
>
> run "make test" (or use ctest directly, e.g. "ctest -VV")
>
> enjoy

Thanks! :-)

- nikolaj