WorldWind Kotlin v1.1.1

• Raise Placemark by the determined Y offset to avoid clipping by the terrain surface.
• Add operator arithmetic functions to Vec2 and Vec3.
• Add variant of Viewport.contains function which works directly with Vec2 object.
• Add variant of WorldWind.cartesianToScreenPoint function which works directly with Vec3 object.
• Add variant of RenderContext.geographicToCartesian function which works directly with Position object.