Add random-colored user avatars + swap username colors

[axiand]

I swapped the username display colors in chat so your own name is blue and others' are grey, for improved readability.

I also made user avatars take on a random color based on the user's ID in messages and the group chat members sidebar. Let me know if everything works, thanks.

[axiand]

Hey, I've tried my best to resolve the merge conflicts by bringing my patches up to date, and applied the component to the private message list as well.

The new ItemAvatarContainer component should be able to integrate anywhere seamlessly, it takes two props: user, which is a valid user object, and size, the width and height of the avatar in pixels.

Again, hoping everything works!