Port KGet to the standard KDE notification system: this means less code, and

Port KGet to the standard KDE notification system: this means less code, and
nicer ways of feedback for the users, who can choose from several types of
notifications for KGet events (like Download added, etc).

The default implementation is configured to use passive popups for all the
events, and for the Added event there is also the sound.

Moreover, the sounds have been converted to OGG.

So, we can make happy a lor of KGet users and close several bugs.

BUGS: 61614, 82287, 94788
CCBUG: 108481

git-svn-id: svn://anonsvn.kde.org/home/kde/trunk/KDE/kdenetwork@435428 283d02a7-25f6-0310-bc7c-ecb5cbfe19da