Precursor to some refactoring planned

- Add hooks to the stanza parsers so that plugins can do additional parsing.
- Change ChatBox instance methods to functions and use them for stanza parsing.
- Move encrypt and decrypt messages to `converse.env.omemo`

Apparently, when receving a 1:1 carbon message, a device was wrongly created
for the contact's device list, instead of our own.

So that `_converse.xmppstatus` is defined before trying to set the
status.

before `converse.initialize` has been called

In the process, remove other "core" promises. There is no core or
community plugins code awaiting on them and since it's possible to
call `converse.initialize` twice, I'm not sure it makes sense to even have them.

Also removed unused error class IllegalMessage.

This element can be used to declaratively insert Converse into the DOM.

You can put `<converse-root>` into the DOM (e.g. by rendering it inside
a React component) before or afer Converse has loaded and/or has been
initialized.

To avoid catching unrelated errors, which can mask other issues in the
code and make debugging more difficult

Otherwise Imgur URLs don't render

Otherwise `isHidden` might return true because `minimized` is set to
`true` but `converse-minimize` is not enabled.

This prevents the burger menu from opening

Currently translated at 99.2% (497 of 501 strings)

Translation: Converse.js/Translations
Translate-URL: https://hosted.weblate.org/projects/conversejs/translations/af/

Also fix i18n typo in src/converse-omemo.js

Also remove top-level i18n declarations in components

Translations called at the top of template files don't apply, since the
trnaslations aren't yet fetched at that point.