Notify the front-end with workers

The problem for which we need solution:

If we import tbx, create new glossary, upload tmx the job is done by a worker. And if the job is completed or there was an error while the job was running in all of the cases the error was logged but the user has no idea on the frontend if something went wrong. The idea is when worker finishes or producess an error in the above listed cases and similar, we should notify the user with some info message.