So that we first render dynamic content (e.g. images) before inserting
it into the chat.
Also, add the `show_images_inline` setting (which is the cause of this
whole change).
Updated tests to handle this new change and start using async/await
instead of promise callbacks.
`toLocaleString` now returns element attributes in alphabetical order
(for better cross-browser consistency).
Also, `toLocaleString` is now used in favor of `outerHTML` because
browsers aren't consistent with one another in their output.
Specifically the methods related to requesting an upload slot and uploading a file.
Also show a progress indicator while a file is being uploaded.
Updates #161
* Use Promises instead of callbacks
* Update to latest (Last Call) version of XEP-0363
* Move non-view specific methods to models instead
* Add more tests
updates #161
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).
