bump version to 1.8.1 (patched by Hypriot)
bump version to 1.8.1 (patched by Hypriot)

dockware/rpi-docker-builder,marsmensch/rpi-docker-builder,hypriot/rpi-docker-builder,moul/rpi-docker-builder,dockware/rpi-docker-builder,marsmensch/rpi-docker-builder