4.0.0 - One-Asset extraction

Changes

• Updated and moved One-Asset to a separate repository
• Small Symlink utility bugfix

3.1.0 - One-Asset

• Encapsulated singleton features in OneAsset directory
• Added UseTypeNameAsFileName to SingletonAssetAttribute
  • This allows descendant classes to be singleton assets without declaring SingletonAssetAttribute
• Added SingletonScriptableObjectFactory
  • This class exposes singleton loading logic so that it can be used with objects that don't inherit from SingletonScriptableObject
• Added new documentation for singleton features
• Added new constructors to UnityDictionary