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This only affects scenarios which do not us group models. Due to
refactoring of the group model the group size distribution is
set by source. This allows different source to spawn different group
sizes.

update the AttributeAgents values to the values in weidmann-1993 and seitz-2016c for all model test scenarios.

update migration assistent such that one can choose from based on which version a project should be reimigrated.

add migration incident to delete an element inside an array, improve the code of the Graph/Tree-class