- Add config variable `muc_show_logs_before_join`
- Restore nickname form for the original use-case (when not showing MAM logs before joining).
- Render nickname form in the `.muc-bottom-panel` when showing MAM logs (instead of in a modal)
- Show a message when there aren't any archived messages to show
- Fix converse-mam so that chat logs are properly fetched before entering a MUC

closes #1266

`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