Change equality comparisons to == and !=

[lilleyse]

Related to this discussion: CesiumGS/cesium#4336 (comment)

If we decide to be loose about type comparisons in the JS implementation we may also want to change === to == to force casting. Right now a style with 5 < "6" would return true but 5 === "5" would be false.

[pjcozzi]

I think I understand that you want to add == and != so that they behave similar to < and friends with type coercion, but why are we removing the JavaScript best practice === and !== operators? Because they can't be implemented with the GLSL transpiler? If so, please explain.

[lilleyse]

Oh I was thinking we would not support both == and === at the same time, but that's definitely doable.

[pjcozzi]

OK, let's do it, thanks.

[pjcozzi]

@lilleyse can you please update this PR and also update the styling spec to include changes needed for point clouds, e.g., pointSize in this PR or a new one?

[lilleyse]

Updated. I'll open a new PR for the other styling and point cloud changes.

[pjcozzi]

Looks good.