T30390 Refactor_multi_label_bool_ops

Summary:
BREAKING!!! What: - Reworked BooleanOperation to support multi label and 3d+t - Changed from class pattern to global functions for generating the mask

Why:

• Functor pattern (class instances configured through contructur) is superfluous and not stateless. Lambdas and global functions are a better approach.
• Added multi label support and allow nary operations (more then two labels at once)

Reworked Boolean widget

+ fixed T30390

Fixed error in selection docu example

Improved visual label selection feedback in QmitkBooleanOperationWidget

Test Plan: code review, gui testing of bool tool

Reviewers: O1 MITK Reviewer Group I, s434n

Reviewed By: O1 MITK Reviewer Group I, s434n

Subscribers: s434n

Maniphest Tasks: T30390

Differential Revision: https://phabricator.mitk.org/D921