Working towards a clean Offline package dependency DAG for data products

[kutschke]

There are a few places in which we have loop dependencies between packages in the Offline repo. Here package refers to a top level dependency. The dependencies are either compile time only or runtime only - there are no link-time dependencies because this would fail the link.

The examples that come to mind now are:

MCDataProducts/inc/SurfaceStep.hh - uses DetectorSystem and GeomHandle.
RecoDataProducts/inc/TrkStrawHitSeed.hh - uses TrackerConditions/inc/DriftInfo.hh and TrackerGeom/inc/Straw.h