extensions/polycode_sandbox: Automagic sandbox wrapper for Polycode's Lua class model - now sandboxed code can subclass classes provided by Polycode
extensions/polycode_sandbox: Sandbox class wrapper: Allow mirroring Polycode's internal class inheritance with minimal effort
extensions/polycode_sandbox: Recursive type checking
extensions/polycode_sandbox: Recursive wrapper method resolver
extensions/{graphics,ui}: Implement event handling class model
extensions/ui: UIElement.hasFocus property
testmodules/minigame: Add "mouse grab" and "clear field" buttons