* Change HASSOS_ID from hassos to haos
Use a rauc install-check hook to make this update compatible with OS
releases using hassos in the compatible string.
* Use home-assistant as organization in CPE_NAME
Align with Home Assistant core which uses home-assistant with a dash as
organization in CPE_NAME.
* Add development build version part to version number
Add third part in the version number to indicate development builds.
Generate a default version number based on the date, e.g.
"5.6.dev20201124".
* Add GitHub Action workflow for development builds
Add another GitHub workflow for development builds. Make it triggered
only for now. The version number is generated by the workflow and
passed to all builds to make sure all builds have the same development
build version.
* Add documentation
Support custom output directories akin to how buildroot supports O=.
This allows to use separate output directory per board, e.g. using
make O=output_odroid-n2.
