[Kget] update for content fetch plugin

[Ningyu Shi]

Hi guys,
    I just worked out a hacky version. The KGet::addTransfer() wrapper
class is implemented. Now the user script can get the source url from
kget, and then ask kget to download what it spits out (call function
in the script), though I'm not quite sure about the QThread part. I'm
kind of busy this week, and will try to work out details when I get
time. I have quite a lot of quesitons for some tiny stuff there, and
will bring them to you later ;)

Thanks
Regards
-- 
Ningyu