Add support for non-linear free flow branch FDs for path based sLTM: currently this is not correctly supported for generating on-the-fly-paths

[MarkRaadsen]

for non linear FF branch of FD the costs on non-blocking link segments vary with flow, but now costs are not updated on non-blocking link segments (because not needed for fixed path set or linear FF branch).

FIX: update costs on all link segments each iteration for generating new paths (but do not mark all those links for tracking necessarily)

Start by creating a test project to be able to easily validate this goes correctly