Refactors the previous "[RN] Cache avatars and provide a default in
case load fails" for the purposes of simplification but also modifies
its functionality at the same time. For example:
- Always displays the default avatar immediately which may be seen if
the remote avatar needs to be downloaded.
- Does not use random colors.
- Uses a default avatar image which is not transparent and ugly but at
least it's the same image that's used on Web. I've started talks to
have images/avatar2.png replaced with a transparent and beautiful
so that will land later on and we'll see the automagic colors in all
their glory then.
00e058d392