T28982 Added option to control MergeStyle and OverwriteStyle of an AutoSegmentationTool

Summary:
+ Also added posibility to the UI to change it.

Added relabel mode to PickingTool

+ Fixed T28982
+ Fixed T29146

Test Plan: code review, test in workbench

Reviewers: O1 MITK Reviewer Group I, kislinsk

Reviewed By: O1 MITK Reviewer Group I, kislinsk

Subscribers: kislinsk

Maniphest Tasks: T29146, T28982

Differential Revision: https://phabricator.mitk.org/D649