Show new messages/forum posts in navigation drawer

Feedback from a user: "It would be good to have a place/notification for all new messages when you first go on the app, instead of separately clicking on contacts or forums and searching for messages."

We should show the number of unread private messages next to the Contacts button on the dashboard, and likewise for forum posts. Bonus points for putting the numbers in little red circles (long ago requested by another user).

Another user requested a timeline of recent activity on the dashboard - for example, this person replied to your post on this forum, or this person shared this forum with you.

Update: We have no dashboard anymore, but might want to show this in the navigation drawer (#431 (closed)).