Optionally extend all tracks to a radius

[EdwardMoyse]

I'm not quite sure how to implement this best, but I just wanted to make note of the problem.

In the ATLAS example, the CombinedInDetTracks have some measurements, and so are not propagated. But they do not reach out to the calorimeter (in turquoise). However the InDetTrackParticles_xAOD have no measurements and so they ARE propagated all the way out. It would be good to be able to optionally extend the first set of tracks too (i.e. make it an option on the collection).