Add tangent generation to new model loader.
Add tangent generation to new model loader.

--HG--
branch : feature/json-loader

nizihabi/engine,playcanvas/engine,SuperStarPL/engine,aidinabedi/playcanvas-engine,sanyaade-teachings/engine,sanyaade-teachings/engine,nizihabi/engine,guycalledfrank/engine,shinate/engine,RainsSoft/engine,horryq/engine-1,shinate/engine,maxwellalive/engine,maxwellalive/engine,horryq/engine-1,aidinabedi/playcanvas-engine,H1Gdev/engine,maxwellalive/engine,guycalledfrank/engine,RainsSoft/engine,shinate/engine,3DGEOM/engine,playcanvas/engine,sereepap2029/playcanvas,MicroWorldwide/PlayCanvas,3DGEOM/engine,sereepap2029/playcanvas,nizihabi/engine,3DGEOM/engine,horryq/engine-1,SuperStarPL/engine,H1Gdev/engine,RainsSoft/engine,sanyaade-teachings/engine,SuperStarPL/engine,MicroWorldwide/PlayCanvas,sereepap2029/playcanvas