Improve notifications

Description of problem:
Right now, users are notified about various things via Uberfire notifications - small pop-up messages. These are quite unfortunate and I'm not sure if they can be improved.
It's a nice widget, but when you get an unexpected notification, it is gone too quick and you are unable to read the message. You might even miss it if you look away for a second. Or you're expecting it, you know what it says because you've seen it hundreds of times and it just blocks you from switching perspectives to continue your work.
It is only usable for very very short messages that the user expects and wants to see - which doesn't happen too often. After some time working with the product, I can honestly say these notifications seriously annoy me.

Perhaps we could have some kind of notification inbox/message tray that would be unobtrusive but easy to get to, where these notifications would stay until you dismiss them.

The idea is to have only that one way of getting notifications, not to have such inbox and the pop-up notifications at the same time.