Fixed #63: fiexed crash when setting uniform argument buffer

[bqlin]

Fixed #63:

• using MTLArgument to get right uniform argument buffer data size;
• generateRenderPipelineState(device:vertexFunctionName:fragmentFunctionName:operationName:) return ShaderUniformSettings directly;
• convertYUVToRGB(pipelineState:uniformSettings:luminanceTexture:chrominanceTexture:secondChrominanceTexture:resultTexture:colorConversionMatrix:) receive ShaderUniformSettings as uniformSettings parameter;