Throw if Plane normal is not normalized

[hpinkos]

I spent a little while this afternoon trying to track down a problem that was caused because someone created a plane where the normal wasn't normalized. The doc says it should be, so I added a DeveloperError check to make sure the normal vector has a magnitude of 1.0.

[bagnell]

Where was the error? Should we also check that it is normalized in the from* functions?

[hpinkos]

My problem wasn't a bug in Cesium, someone made a mistake using Plane in another app. I just think throwing a DeveloperError here is helpful so next time it'll point out the mistake immediately.

[hpinkos]

And I don't think we need to put the check in the from functions because they each call new Plane

[bagnell]

And I don't think we need to put the check in the from functions because they each call new Plane

Only when a result parameter isn't supplied.

[hpinkos]

Good point, I'll update that

[bagnell]

My problem wasn't a bug in Cesium

Ok, I agree this is a good change.

[hpinkos]

@bagnell ready

[pjcozzi]

Please document the @exception.

[hpinkos]

@pjcozzi done