Onboarding, Command UI improvements, Any colour theme

* Custom any colour theme (Android 11+)
* Collapse empty thread selector while typing
* Back exits single thread view
* Offer cheogram.com register on first setup if no PSTN or SMS gateway
* Offer to set up dialler integration when new PSTN gateway detected
* Get mic permission when setting up dialler integration
* Show very wide tables as list of cards
* Change notification LED colour to perpy
* Support custom actions defined by list-single var=http://jabber.org/protocol/commands#actions
* Render a form with only one list-single or boolean as buttons
* Allow creating an account for yourself using an invite
* Fix nested scroll on ListView in Command UI
* Remove RoundedImageView dependency
* Menu item to save image (or inline image) as sticker
* Extended addressing ofrom notifications should look like MUC (group text)