Window::has_focus
unsafe
* Use objc2::foundation CG types * Add safe abstraction over UIApplication * Add safe abstraction over UIDevice * Add safe abstraction over UIScreen * Add safe abstraction over UIWindow * Add safe abstraction over UIViewController * Add safe abstraction over UIView * Appease clippy
* Begin abstraction over UIKit * Clean up UIWindow override declaration * Clean up UIApplication delegate declaration * Clean up UIViewController override declaration * Finalize objc -> objc2 rename