Huge optimizations of glTF animations, pool of scenes for FPS game, limited PBR specu

[DP News-Robot]

With the help from Valgrind, I made a few significant optimizations to the engine animations, in particular affecting the skinned animation of glTF: We update VBOs during animations much faster (we upload it more directly when possible, without recalculating some useless structures along the way). Some primitives are kept in GPU much better (previously we …