Removed `_converse.chatboxviews.showChat` and trying to simplify how
chats are created and when they're shown.

Prompted by the work to split the MUC views into a separate plugin

- Remove undocumented and unused event `update-status-ui`
- Remove xhr_custom_status and xhr_custom_status_url options
- Use default value
- Remove unnecessary getter and setter

* Update jslicenses-inverse.html

* Update inverse.html

* Update index.html

* Update mobile.html

* Update anonymous.html

* Update CHANGES.md

It depends on `eval` which is unsafe.

Otherwise we lose the MUC session upon reload.