v0.4

Jumbo release:

• New object lookup system
• Convenience for NodePath
• Utility functions exposed
• Vararg support in methods
• Lots of bug fixes in the binding to deal with Godot idiosyncrasies.
• No longer surfaces GString, instead hides the Godot string everywhere and surfaces a Swift string
• Implementation of Packed* and their indexers
• Types are now hashable
• Handles subclasses of Ref
• Documentation upgrade
• Annotate some methods with @discardableResult
• Signals are now surfaced in the API
• Indexers for dictionaries