v0.14

• New implementation of sets and dictionaries (faster and partially order-preserving)
• else block for loops
• Null-conditional slicing: x?[a:b:c]
• Removed is null and is not null operators in favour of standard comparison with null
• Removed in operator in favour of new has method for containers
• Minor changes regarding methods of the built-in types
• Some changes in the support of escape sequences for special characters
• A few bugfixes regarding type checking and other improvements