Some changes on T&L (shade mapping)

* Cleaned up formatting in the fragementshader a bit
* Init unlitcolor with u_matambiant if there is no color (HW)
* Changing shade mapping: don't handle the shademapping lights alongside to other lights and adjusting the uv coords to `0.5*dot(lightpos, normal) + 0.5`
(mainly tested with celshading demo as it uses shademapping for texturing)