Feature/osg shader light fix

default type was directionnal
https://github.com/cedricpinson/osgjs/blob/0ebf37b0bb30f6d1e81bd5b0ed9f487385e2972b/sources/osg/Light.js look at the position [0,0,1,0] the position[3] was 0 and it means it was directional.
I did not check about the falloff but could you check and update to have same kind of behavior as before.