Groups have a new method `alignIn`. It allows you to align the Group within another Game Object, or a Rectangle. You can specify one of 9 positions which are the new position constants such as: `Phaser.TOP_LEFT` or `Phaser.CENTER` (see docs for the complete list). The Groups are positioned based on their child bounds, which takes rotation and scaling into consideration. You can easily place Groups into the corners of the screen, or game world, or align them within other Sprites, using this method.
Groups have a new method `alignTo`. It allows you to align a Group to the side of another Game Object, or a Rectangle. You can specify one of 11 positions which are the new position constants such as: `Phaser.TOP_LEFT` or `Phaser.LEFT_BOTTOM` (see docs for the complete list). The Groups are positioned based on their child bounds, which takes rotation and scaling into consideration. You can easily align Groups next to other Sprites using this method.
ArcadePhysics.Body.onOverlap is a new Signal that is dispatched whenever the Body overlaps with another Body. Due to the potentially high volume of signals this could create it is disabled by default. To use this feature set this property to a Phaser.Signal: `sprite.body.onOverlap = new Phaser.Signal()` and it will be called when an overlap happens, passing two arguments: the sprites which collided.
ArcadePhysics.World.separateCircle is a new method that handles all circular body collisions internally within Arcade Physics (thanks @VitaZheltyakov)
All of the Arcade Physics internal methods, such as `collideGroupVsSelf`, `collideSpriteVsSprite` and so on, have been updated to work with circular body shapes (thanks @VitaZheltyakov)
ArcadePhysics.Body.onWorldBounds is a new Signal that is dispatched whenever the Body collides with the world bounds, something that was previously difficult to detect. Due to the potentially high volume of signals this could create it is disabled by default. To use this feature set this property to a Phaser.Signal: `sprite.body.onWorldBounds = new Phaser.Signal()` and it will be called when a collision happens, passing one argument: the sprite on which it occurred.
* The PIXI.BaseTexture.imageUrl property has been removed, as it was never actually populated.
* The PIXI.BaseTexture._UID property has been removed, as it was never actually used internally.
* All references to PIXI.BaseTextureCache have been removed (primarily from BaseTexture.destroy and Texture.destroy), as the BaseTextureCache was never used internally by Phaser, or by our custom version of Pixi.
* PIXI.TextureCache has been removed. It was only ever used by the __default and __missing images that Phaser generates on start-up. It wasn't used internally by Phaser anywhere else, and the only references Pixi has to it have all been removed. If you need it in your own game, please refactor it to avoid it, or re-create the object on the PIXI global object.
* Canvases created by `BaseTexture.fromCanvas` no longer have the `_pixiId` property attached to them, as this was never used internally by Phaser or Pixi.
* PIXI.BaseTexture.updateSourceImage is now deprecated. Please use `Sprite.loadTexture` instead.
* The property PIXI.BaseTextureCacheIdGenerator has been removed, as it is no longer used internally by Phaser or Pixi.
* PIXI.Texture.addTextureToCache has been removed. The PIXI Texture Cache was never actually used by Phaser, and was leading to complications internally.
* PIXI.Texture.removeTextureFromCache has been removed. The PIXI Texture Cache was never actually used by Phaser, and was leading to complications internally.
* PIXI.Texture.fromFrame and PIXI.Sprite.fromFrame have been removed. They relied on the PIXI Texture Cache, which was never actually used by Phaser, and was never used internally by Pixi either.
* The property PIXI.TextureCacheIdGenerator has been removed, as it was not used internally.
* The property PIXI.FrameCache has been removed, as it was not used internally.
* The missing image texture, for when an image has failed to load, is now available under `Phaser.Cache.MISSING`.
* Phaser.Cache.addImage will now check the key given, and if `__default` or `__missing` it will update the new consts `Phaser.Cache.DEFAULT` and `Phaser.Cache.MISSING` accordingly, allowing you to replace the default or missing image textures used by Phaser.
* Phaser.Cache.getPixiTexture has now been removed, as the Pixi Cache isn't used internally anywhere any longer.
* Phaser.Cache.getPixiBaseTexture has now been removed, as the Pixi Cache isn't used internally anywhere any longer.
Graphics objects enabled for input would fail to do anything if a Phaser Polygon was given to the Graphics object (which it was in nearly all cases), as it wouldn't detect input correctly with flattened polygons (thanks @symbiane #2591)
