* always use http for apt repos
* pass possible proxy arguments to docker
* populate lower-case env variables with upper-case ones if not set otherwise
- Replace creation of `armbian-config.list` with
`armbian-config.sources`. This holds the same information in a newer
format, deb822. This does not affect `armbian.list`.
See also: https://github.com/armbian/configng/pull/407
* Refactor armbian-config into install as external package
- https://github.armbian.com/configng repository is always present
- package can still be removed from the install list
Since this tool will have deeper integration with Armbian, we should probably drop possibility to remove the tool from the list.
* Enable armbian-config as extension
