Add Atan2 to expose expressions

Can you expand the expose system to use trigonometry like atan2?? This can be very useful for spawning objects with the brush. That way we could find the direction between prevPosition and Position and rotate objects to face in a certain direction.

https://forum.unity.com/threads/unity-awards-nominee-mapmagic-2-infinite-procedural-land-generator.875470/page-38#post-8011130