Rework Iteration Class

[Carsten Uhlig]

Rework the iteration class, so that in general we can use it with a script and update it (mergedannotations, etc.)

todo

• include merged annotations
• PrepareDatasetPipeline specific to mutations, etc. (make subclasses)
• featuregenerators in constructor
• automatic recalculation of missing iterations

@abojchevski please add tasks that must be done
@jmcejuela when you see something that should be changed, add this to the list

[Dr. Juan Miguel Cejuela]

I mark this as deprecated. We actually have already the script run_iteration.py