This prevents it from being persisted across page loads and makes more
sense logically.
Also move markScrolled to utils and MUC unread messages indicator to bottom panel.
Instead of on the views/components.
We still have `close` methods on the components, but they are just
event handlers and not external API methods to be called by other code.
Instead `close` should be called on the model.
More work on making bottom panel sub-components declarative
- Handle auto-completion in the converse-muc-message-form element
- Make message limit indicator a component
- Rename template
