Show Room avatars (in the RoomsList) for direct rooms

[kevinaboos]

Currently the RoomsList does not display avatar images for "direct" rooms (direct messages / person-to-person chats).

I'm not sure of the exact cause, but I would assume that the direct rooms themselves don't have an established Room Avatar, and that most clients are just using the other person's individual user Avatar as the room avatar. Not sure how that would work with direct rooms that include more than two members... but that could also be explored as part of this issue, or left for another issue in the future.

See the following, in which every room (except "Testing" and "Testing2") should have avatar images.