Bug fixes

• 4a08d33: Fix nameof on single expression names, reported by AirGamer
• 31bda21: Fix compile issues with Unity versions > 2018.4.20 due to Unity introducing a namespace named SyntaxTree, reported by @ResourceHog in #38
• 3f66877: Fix issue with array creation expressions incorrectly converting types in some cases
• 7e2b5ae: Fix issue where empty string interpolations would leave old values in variables, reported by @ikuko in #40
• 64c8d3e: Reuse the UdonEditorInterface for slight improvement in compile performance and preventing a regression in compile performance in newer SDK's
• d52ce00: Fix copy elision assigning intermediate values to a variable in some cases, reported by @ikuko in #41