Resolve "Merge dashboard and dashboard-backend repos"

Closes #33 (closed) Addresses #71 (closed)

I'd like to make a second MR that updates the image references in the helm chart. The reason why I'd like to split those two, is that this MR includes 200 commits from another repository.

The only relevant changes I did is merging the .gitlab-ci.yml files from these two repositories. Other than that I only made a branch in the back-end repo that contains all the files inside a back-end folder, added that as a remote in this repo, and merged it into this branch. This way we keep commit history and authorship.