[packagekit] box and zypp backends

[Richard Hughes]

I've edited the box and zypp backends to use the new PkFilter code
that's in git rather than the copy-paste code that was there before. I
think I've done it correctly, but please can one of you guys do a test
compile to make sure I've not missed anything.

Marcin, you probably also want to use the same code for poldek. if you
do "git-show 0292958ffe40d4f1273d16e8c8e86ceb04abc587" then that should
give you enough pointers. Thanks.

Thanks,

Richard.