add node transformation API

Signed-off-by: Wayne Wolf <wayne.ron.wu@googlemail>
Create a new root node

the original root node comes from blender assimp has different y,z
orientation, create a new root node with y axis up to be consistent
with OpenGL.

Signed-off-by: Wayne Wolf <wayne.ron.wu@googlemail>
Move node

Signed-off-by: Wayne Wolf <wayne.ron.wu@googlemail>