Notifications you can actually scan

The notifications page was a run of near-identical paragraphs. It has been redesigned.

New notifications are now grouped at the top and marked, so you can see what has changed since you last looked without re-reading things you have already dealt with. Everything else sits under "Earlier".

Each notification is labelled by what it is about -- Mentorship, Session, Feedback, Jobs, Projects, Skill Labs, Community -- and shows when it happened in plain terms ("2 hours ago") rather than a bare date.

One small thing we were careful about: the page still marks everything read when you open it, but the "New" group is worked out the moment the page loads, so it does not empty itself while you are looking at it.