Experimental game-oriented toolkit for Kore

Adds some convenience, structure and basic functionality probably useful for games to the base Kore framework.

• Base implementation of a game class ("KoreGame") with convenient lifecycle callback hooks.
• Fast, flexible "opportunistic batching" drawing class (Gfx) to gather geometry into a batch and submit as one draw call only when relevant draw state changes.
• Convenient quad sprite rendering
• Support for rendering with arbitrary shaders, vertex formats, geometry (BYO triangle generation)
• Loading of TexturePacker XML atlases
• Scene structure

Currently comes with a sample scene that implements a BunnyMark style stress test. Scores around 32,000 bunnies on an iPhone 6s using a non-optimised draw loop.

Check out source to your development machine. Update the Kore submodules. Use the standard Kore 'make' procedure to generate project files for your IDEs.

Tested on MacOS and iOS.

Highly experimental! Your comments and suggestions are welcome :)