Make notifications look as nice as deprecated Activity Stream

The new notifications feature brought some nice new things but I feel strongly that the UI is way less nice than what we used to have with the Activity Stream and that's an important usability regression to me.

I know that tastes and colors is something subjective so please let me know if you disagree with this statement!

So this issue is about making it look nice again.

See screenshots showing my profile on xwiki.org (pre notif) and on myxwiki.org (post notif), to see the visual difference.