Send list of typing user IDs as 'user_ids' list within 'content', so that m.typing stream events have a toplevel content, for consistency with others

Actually auth-check to ensure people can only send typing notifications for rooms they're actually in

Media repository

Allow only one download for a given image at a time, so that we don't end up downloading the same image twice if two clients request a remote image at the same time

Limit the size of images that are thumbnailed serverside. Limit the size of file that a server will download from a remote server

Federation retries

turn back on per-request transaction retries, so that every time we try to hit a dead server we actually end up hammering 5 times :|