work on #113
	renamed:    build-steps.d/2400_convert-img-to-vdi -> build-steps.d/2500_convert-img-to-vdi
	renamed:    build-steps.d/2500_create-vbox-vm -> build-steps.d/2600_create-vbox-vm
	renamed:    build-steps.d/2600_export-vbox-vm -> build-steps.d/2700_export-vbox-vm
work on #113
Deactivated running update-command-not-found during build, since not deterministic. Manually running of course still possible.
work on #113
Merge remote-tracking branch 'origin/master'
Merge remote-tracking branch 'adregithub/master'