Camera Fix

[lilleyse]

Fixes #3178

Only the last change was required to fix the problem, but the others looked similar enough that I changed them too. Another approach is normalizing the direction, up, and right vectors in Camera.updateMembers to catch all cases of this happening, like:

var direction = camera._direction;
var directionChanged = !Cartesian3.equals(direction, camera.direction);
if (directionChanged) {
    direction = Cartesian3.normalize(camera.direction, camera._direction);
}

[pjcozzi]

Update CHANGES.md.

Is it possible to add a reasonable test to verify that the vectors are orthonormal?

@bagnell merge when you are happy.

[lilleyse]

I believe that's already happening here: https://github.com/AnalyticalGraphicsInc/cesium/blob/master/Source/Scene/Camera.js#L490-L506 but maybe the logic requires the vectors to be normalized before hand.

[lilleyse]

Oh.. do you mean a spec test?

[pjcozzi]

Yes, for the unit tests.

[lilleyse]

I removed this line because it wasn't actually doing anything. It only passed before because (0,0,-0.999999) did not equal (0,0,-1.0). Or maybe it should be checking .toEqual instead of .not.toEqual?