SoftGpu: Fix (?) texture coordinate reading for through mode. Needs review.
SoftGpu: Cleanup depth testing and only account for the clearmode depth write flag if clearmode is enabled.
SoftGpu: Add the most awesome color class there is and vastly simplify texture functions with it.
SoftGpu: Implement alpha blending.
SoftGpu: Workaround a bug in through mode (in Rasterizer::DrawTriangle den would become really large because clippos.w wasn't initialized to a good value).