T30417-Fix_confusing_highlighting_invisible_labels
Summary:
Introduced the LabelHighlightGuard
Rework mapper to support highlight invisible
Refactored QmitkMultiLabelInspector to use the highlight guard
+ Fixed T30417
+ Added documentation
Test Plan: code review, UI test (pressed shift key shows hidden highlighted labels)
Reviewers: O1 MITK Reviewer Group I, kislinsk
Reviewed By: O1 MITK Reviewer Group I, kislinsk
Subscribers: kislinsk
Maniphest Tasks: T30417
Differential Revision: https://phabricator.mitk.org/D949