Moved BitmapData and RenderTexture into the textures folder for now.
All Game Objects now have their own sub-folder, with their Factory and renderer functions alongside them, plus any other files they need.
New Factory class added. Currently hooked into `game.factory` for testing, but will swap to `game.add` when complete.
Emitter.setAlpha has a new 'rate' parameter which allows particles to change alpha over time, using any Easing value or timescale.
Emitter.bringToTop and Emitter.sendToBack are booleans that let you optionally set the display order of the Particle when emitted.
Emitter.particleAnchor allows you to control the anchor of emitted Particles. Defaults to 0.5 (same as before) but now under your control.
Emitter now emits Phaser.Particle objects instead of Phaser.Sprites, which can be extended as required.
Emitter has had various local properties removed that were already declared in Phaser.Group which it extends.
