TR2-TR3 Skyboxes fixed for TEN by Heckler89

Description
This is a pack of skyboxes fixed for TEN

Skyboxes from TR2 and TR3 have rotation and height issues in TEN so I took the liberty of fixing them to work without scripting

All meshes and textures are ripped directly from legacy TR2 and TR3

Note
Credits:
- Core Design
- Hecker89
- The Tomb Engine team