Use one event instead of two, by listening to `num_unread` on chatboxes.

New in the sense that we haven't seen them before

due to Awesomplete doing things to the DOM and then confusing Snabbdom.

Currently only allows enabling an "App Service", based on pass-in
configuration values.

when we received a message for a yet non-existing chat in singleton
mode.

This is a workaround until we have support for XEP-0198

updates #1111

Calling `remove` without models does nothing

updates #1068

so that you can navigate "back" to the controlbox.

updates #1107

instead of disabling the plugin immediately.

This allows us to change the view_mode dynamically.

Fixes #1072

updates #1072

Otherwise we might have stale disco info and no way to invalidate the cache.

fixes #1106