Partial spies and 2018.2.4 support

• Can now generate a 'partial spy'. A partial spy offers the option to forward invocations to the original implementation. Only works for test doubles which inherit from a class.
• Dummies now generate a fatal error when a default value cannot be derived since dummies are only really meant as placeholders.
• Tuple argument labels are preserved and accessible when using the invoked parameter properties.
• Supports AppCode 2018.2.4.