So that we first render dynamic content (e.g. images) before inserting
it into the chat.
Also, add the `show_images_inline` setting (which is the cause of this
whole change).
Updated tests to handle this new change and start using async/await
instead of promise callbacks.
We now have uniform avatar rendering for the profile, messages and
chatboxes.
By rendering as canvas, we can avoid stretching the image.
In the process I also moved the ChatBoxViews collection into its own
plugin `converse-chatboxviews` and placed the AvatarAware views there.
fixes#1157
