https://xmpp.org/extensions/xep-0198.html#resumption

The <resume/> element MUST include a 'previd' attribute whose value
is the SM-ID of the former stream and MUST include an 'h' attribute
that identifies the sequence number of the last handled stanza sent
over the former stream from the server to the client.

- Set roster_fetched flag when we get an empty IQ[type="result"] stanza
- Set `restored` flag when resuming in converse-smacks
- Don't trigger change event when fetching xmppstatus values
- Removed two events, since we can just listen to `change` on `_converse.xmppstatus`.

- Test for info message indicating a configuration change
- Test that the MUC reconnects when a `not-acceptable` error is returned

instead of on the view.

Other types of messages such as `error` don't necessarily have a JID
tied to them.

Also, remove ephemeral messages after 10 seconds, not 20

Use-case is when an invalid MUC gets opened in singleton mode.
Without this fix a new chat with spinner appears, even though it
shouldn't.

updates #555

- Remove the `keepalive` configuration setting. It is now always implicitly `true`.
- Remove the `expose_rid_and_sid` configuration setting.
- A `prebind_url` is now mandatory when setting `authentication` to `prebind`.
- It's no longer possible to pass in `rid` and `sid` values to `converse.initialize.

I'm using prettierx, which is a fork of prettier so that we can have
spaces before the brackets in a function declaration.

I don't like how restrictive prettier is concerning its configuration
and formatting.

- it messes up some indentation in specs/
- it removes a second newline when I specifically want to have two
- it doesn't allow spaces before brackets in function declarations (hence prettierx)
- it adds spaces for function parameters with default values

None of this is configurable.

So auto-formatting is not turned on by default, but it might be a useful
tool in some cases.

Fixes an issue where indentation was off in converse-core.js, causing
vim-sleuth to wrongly indent by three spaces only.

- fix import path
- remove unnecessary lines in webpack config
- remove unused file

updates #1111

* Checkmark and edit modal button are now on the right
* Instead of showing checkmarks for MUC messages,
  we now show them as light grey before MUC reflection
* Simplify message markup by requiring less `if` statements

Also, set the resource in `setUserJID`