Integrate reconstruction from timeslice data and from digi data (simulation).

This MR enables to use the CbmReco steering class also for input data on digi level, either from simulation or from a previous unpacking stage. The difference in digi format (direct digi branches if from simulation, CbmDigiTimeslice if from unpacking) is accounted for by the tasks.

If the input source extension is ".root", CbmReco uses FairFileSource instead of CbmSourceTs, and skips the unpacking task.