Updated DetectionTask.java: implemented the Grouper and EqualityTester
subclasses within the subtasks IndexCullerBySize.java,
IndexCullerByHash.java and within the method groupFilesByHash(..).
Merge branch 'implement_EqualityTester' into add_ui_components_and_behavior
Implemented Profile.java and ProfileBuilder.java.
Merge branch 'implement_ProfileBuilder' into add_ui_components_and_behavior
Embarrasingly neglected to add FileHasher.java to the repo.