Minor features and bug fixes

• e5c53f5: Add support for expression-bodied methods, reported by @naqtn
• cd6b89b: Add support for NonSerialized field attribute, requested by AirGamer
• 87e6bda: More strict class name replacement on U# template script creation, reported by Sacchan
• a210e0e: Set public strings to an empty string instead of null to match Unity's behavior, reported by @TheHelpfulHelper