Sounds

We have sounds in our repo for a long time, but nobody used them, till now.

I implemented the sounds as soundpacks (themes), so the sounds from our sound directory are a "default pack" and have to moved into the soundpack directory (by installer?): ``` QStandardPaths::writableLocation(QStandardPaths::ConfigLocation) + '/' + AppInfo::name + "/sounds" ```

I did the pack handling different from the smileypacks, if it's better in this way, I'll change the smileypack, too.