Originally, I tried to adapt the existing (but in various ways broken)
Dijkstra implementation in `storm::utility::graph::performDijkstra`,
but that proved to be more cumbersome (mostly because of the behaviour on
initial states) than simply rolling my own -- so that's what I
eventually did.
Former-commit-id: 33b2be8067 [formerly 0d5c507568]
Former-commit-id: b35fc0bee3