Add focal-based CI docker images
This adds focal CI images (at least for native building).
Differences compared to 16.04 CI image:
- Clickable is installed from PPA again
- Less packages installed via apt, that have been needed for building python, I think:
- libbluetooth-dev
- tk-dev
- uuid-dev
- wget
- ca-certificates
- build-essential
- libssl-dev
- libffi-dev
On reviewing please look at the diff between 16.04 and 20.04 CI images.
Supports clickable#277 (closed)
Edited by Jonatan Hatakeyama Zeidler