update content of 'contributing.md'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update content of 'Vagrantfile'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update content of 'params.pp'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update content of 'params.pp'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update content of 'params.pp'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>
update content of 'metadata.json'

Signed-off-by: Sebastien Varrette <sebastien.varrette@uni.lu>