i am not sure, what the intention of subsite::pivot_root actually is, since it just flips the package associated with a node_id, but lets e.g. the node-hierarchy unchanged. Since this function had already a couple of TODOs, and it is actually not clear, to what extend the subsite should/most be flipped, i added more potential TODOs to it. Since makes at least clear what the function does not do (yet).
