Fix tangent/bitangent when stRotation is applied

[hpinkos]

Polygon and ellipse were both computing tangent and bitangent incorrectly when the stRotation option was used. This is because stRotation is being applied clockwise and the rotation to the tangent/bitangent was being applied counter-clockwise.

Before:

After:

Ellipse sample code

Polygon sample code

[cesium-concierge]

Thanks for the pull request @hpinkos!

• ✔️ Signed CLA found.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

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[bagnell]

Good catch.