Previously we kept all entities and their items (which are also
instances of _converse.DiscoEntity) in a flat array.

Instead, we should have a tree-like structure where items are stored
on the relevant entity (and recursively on other items).

If "inVerse" is renamed to "fullscreen" then "inVerse" in the fullscreen.html file should be renamed to "Converse"?

This reverts commit 7303e96c.

Instead of dropping the feature entirely, we can check if the CSN is a
carbon message.

To avoid showing them erroneously would mean keeping track of used
message ids which seems like more work than justified by the feature.

Fixes #1026

To more cleanly separate views and models and to make MUC in headless
mode more viable.

Refs #1032

* Distinguish between CSN messages and other types of messages
* Properly clear previous notifications
* Better handling of notifications from multiple users (in MUC)
* Rename methods to make clarify intent

* replace geoURIs by link to openstreetmap

* Added testcase

They don’t have an automated redirection, nor HSTS preload, so it is
better to directly point to the HTTPS version of their website.

Thanks to @linkmauve

and out of the MUC views plugin.

Refs #1032

* checkForReservedNick
* parseRoomFeatures
* sendConfiguration

Refs #1032

The theme is still bootstrap3 based and there isn't enough time
currently to redo on bootstrap4.