Added missing Decal.setRotation method.

[nooone]

http://stackoverflow.com/questions/24632095/how-to-rotate-decal-over-more-then-one-axis-at-moment

It looks like currently the only way to set a rotation on all axes at the same time is via a workaround like this:

decal.setRotationX(0);
decal.setRotationY(0);
decal.setRotationZ(0);
decal.rotateX(angleX);
decal.rotateY(angleY);
decal.rotateZ(angleZ);

Or the shorter but more ugly version:

decal.setRotationX(angleX);
decal.rotateY(angleY);
decal.rotateZ(angleZ);

That's why I added a Decal.setRotation(...) method which can set all angles at once.

[xoppa]

Please rename the arguments to yaw pitch and roll (and use the comment to specify which axis it is)