Move sky/examples to sky/sdk/lib/example, and code changes to support that change. Fixes T277.

sky/examples/game/lib/texture.dart

-part of sprites;
-
-/// A texture represents a rectangular area of an image and is typically used to draw a sprite to the screen.
-///
-/// Normally you get a reference to a texture from a [SpriteSheet], but you can also create one from an [Image].
-class Texture {
-  /// The image that this texture is a part of.
-  ///
-  ///     var textureImage = myTexture.image;
-  final Image image;
-
-  /// The logical size of the texture, before being trimmed by the texture packer.
-  ///
-  ///     var textureSize = myTexture.size;
-  final Size size;
-
-  /// The name of the image acts as a tag when acquiring a reference to it.
-  ///
-  ///     myTexture.name = "new_texture_name";
-  String name;
-
-  /// The texture was rotated 90 degrees when being packed into a sprite sheet.
-  ///
-  ///     if (myTexture.rotated) drawRotated();
-  final bool rotated;
-
-  /// The texture was trimmed when being packed into a sprite sheet.
-  ///
-  ///     bool trimmed = myTexture.trimmed
-  final bool trimmed;
-
-  /// The frame of the trimmed texture inside the image.
-  ///
-  ///     Rect frame = myTexture.frame;
-  final Rect frame;
-
-  /// The offset and size of the trimmed texture inside the image.
-  ///
-  /// Position represents the offset from the logical [size], the size of the rect represents the size of the trimmed
-  /// texture.
-  ///
-  ///     Rect spriteSourceSize = myTexture.spriteSourceSize;
-  final Rect spriteSourceSize;
-
-  /// The default pivot point for this texture. When creating a [Sprite] from the texture, this is the pivot point that
-  /// will be used.
-  ///
-  ///     myTexture.pivot = new Point(0.5, 0.5);
-  Point pivot;
-
-  /// Creates a new texture from an [Image] object.
-  ///
-  ///     var myTexture = new Texture(myImage);
-  Texture(Image image) :
-    size = new Size(image.width.toDouble(), image.height.toDouble()),
-    image = image,
-    trimmed = false,
-    rotated = false,
-    frame = new Rect.fromLTRB(0.0, 0.0, image.width.toDouble(), image.height.toDouble()),
-    spriteSourceSize = new Rect.fromLTRB(0.0, 0.0, image.width.toDouble(), image.height.toDouble()),
-    pivot = new Point(0.5, 0.5);
-
-
-  Texture._fromSpriteFrame(this.image, this.name, this.size, this.rotated, this.trimmed, this.frame,
-                           this.spriteSourceSize, this.pivot) {
-  }
-
-//  Texture textureFromRect(Rect rect, [String name = null]) {
-//    assert(rect != null);
-//    Rect frame = new Rect.fromLTRB();
-//    return new Texture._fromSpriteFrame(image, name, rect.size, false, false, );
-//  }
-}