`streamFeaturesAdded` should only be triggered once we've received them
from the server.

This appears to be a timing bug, likely introduced by the IndexedDB
refactoring.

- Retracted moderated message are not editable
- Use "removed" for user-facing text

not while tearing down, otherwise the modals get removed while
reconnecting and we have stale references to modals no longer in the
DOM.

- Add support for switching ephemerality after message creation
- Move more methods from ChatBox and ChatRoom to utils/stanza.js
- Rename 'ephemeral' to 'is_ephemeral' since it's a boolean

as opposed to having them in the `u` object

So that we don't need to `_converse` obj in order to log messages

also recommendation to enable smacks

Use `float:left` instead of flexbox

1. enable avatars in autocomplete
2. change search/filter type for automcomplete

Fixes #1769

- Move headless one-on-one chat functionality into converse-chat
- Split converse-headline into converse-headlines and converse-headlines-views
- Add api in `_converse.api.chatboxes` for creating chatboxes
- Add `_converse.api.controlbox.get` method