The eventual goal is to avoid UI-related stanza processing if the relevant chats
aren't in the DOM.
With the current architecture, chatboxes are created (and the stanzas
related to them processed) even if `#conversejs` isn't in the DOM.
* Initial work on making controlbox an element
* Create a shared base class
* Ceate ChatBoxViews proxy
* Update sass now that certain classes are moved to converse-chats element
- Combine all test init functions into `initConverse`
- Use `async` functions in more tests
- Replace `var` with `let` and `const` in more tests
- New utils method `toStanza` which converts a string to a Node
`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.
- Move `getDefaultNickName` to the model and rename to `getDefaultNick`
- Let `checkForReservedNick` return a promise and save `nick` once received
- Updated `openAndEnterChatRoom` to wait appropriately and remove presence-wrapper
- Update tests to wait appropriately
- Remove presence-wrapper in `getRoomFeatures`