responsible for showing messages based on the extended presence information.

- Use DOM API instead of jQuery
- Make info messages overridable (allows also for disabling them)
- Break up large function with inline callbacks into smaller ones

Via `rooms.open` API method.

together with keepalive.

This is necessary for cleaning up after tests (now that each test has its own
initialized converse).

Should hopefully not cause any issues when logging out during normal use.

and don't show the online count in the toggle.

Otherwise RosterContactView objects stay around and keep on listening.

Only a small subset of tests currently working with this.

To allow for better template customization.

- Remove groupviews, so that they'll get recreated upon reconnection
- Don't call `clearSession` when reconnecting. We want to reuse the
  Backbone collections.
- Emit `rosterInitialized` event and use that in converse-rosterview.js
  (instead of overriding).
- Refactor `onReconnected` to emit `rosterReadyAfterReconnection`, call
  `converse.populateRoster()` and `converse.chatboxes.onConnected()`.
- Recreate the roster view on the `rosterReadyAfterReconnection` event.

It's not used and confuses people. Instead the message gets inserted via
`$.text`, to avoid injection attacks.

updates #714