Added missing package __init__.

This is a tiny fix that was necessary to have a proper pip install of the north package.

Please merge after review.

requested review from @sanbrock

Yes, I have found it and can also confirm that the change works fine as being integrated as a submodule in nomad. Note that the submodule reference tag in 'nomad' can also be then updated to point to somewhere on 'develop'. LGTM

approved this merge request

mentioned in commit f9063215

merged