Expose individual steps of track reconstruction in full_chain python scripts

Discussing the easier way for EF Tracking people to play with ACTS it turned out that it would be beneficial to expose reconstruction pipeline in mode details in the top level scripts (at least for the ITK).
Having a script where all the steps are clearly visible would encourage people to play with it (e.g. replace one module).
The configuration as is (especially seeding) is quite convoluted and general. Presumably we talk here about one workflow with:
data prep. -> clusterisation -> sp making -> seeding -> CKF and the candidate to play with is seeding.

This issue is realy to hear opinions about it.