OBJLoader now support transparency

Mesh::AddSubMesh no longer return bool

Former-commit-id: 71217618d179c5853683f4615901565cb7cd3ab8

include/Nazara/Renderer/Material.hpp

@@ -21,7 +21,11 @@
 
 struct NAZARA_API NzMaterialParams
 {
+	bool loadAlphaMap = true;
 	bool loadDiffuseMap = true;
+	bool loadEmissiveMap = true;
+	bool loadHeightMap = true;
+	bool loadNormalMap = true;
 	bool loadSpecularMap = true;
 
 	bool IsValid() const;