LitterBox Version 1.6

This release includes:

• Code Perfumes! (see README.md)
• Initial support for search-based refactoring
• Added metrics: Dr. Scratch Computational Thinking Scores
• Added metrics: Halstead metrics
• Added metrics: Interprocedural Cyclomatic Complexity
• Reworked dependency analysis
• Refactoring: Support for Scratch extensions
• Refactoring: Metadata
• Bugfixes and cleanups
• Updated descriptions