Attempt to fix continous integration

Finally, the version bump

changelog and documentation

bump version to 0.6.3

Add purism form factor information

Revert the default painting algo to the former one

add correct release date for 0.6.1

Bump version and update release date (fix maoschanz#214)

and add screenshots

and update debian package config (maoschanz#196)

Scrumptious black backgrounds to try to please appstream-util validate

Minor bug related to a recent renaming of a method