v0.3.0-alpha.4

• Shaders now support goto-like statements (break, continue, early returns)
• Started a renderer rewrite
• Added IMask:
  • allows per-pixel masking when rendering
  • can be written to and read from directly or filled in using a canvas (see IMask[int x, int y] and ICanvas.WriteMask)
  • Created using Graphics.CreateMask
• Added IDepthMask:
  • does everything a regular mask does, plus depth testing (useful in 3d rendering)
  • pass to ICanvas.Mask(IMask) to enable depth test. The IDepthMask.Comparison property configures the comparison used
  • pass to ICanvas.WriteMask(IMask) to enable depth write.
  • don't forget to call IDepthMask.Clear(1f) each frame before rendering!
• Started the IGeometry api:
  • an IGeometry is a read-only shape or model
  • can be created via Graphics.CreateGeometry and rendered using ICanvas.DrawGeometry
• renamed TileMode to WrapMode
• ITexture.GetPixel and ITexture.SetPixel are now obselete in favor of the new texture indexer ITexture[int x, int y]
• Fixed many, many bugs