[#88][#66][#76]CE 3.5+ Compatibility

- Cleaned up large functions in export.py.
- Made some improvements to material/texture export.
- ExportNodes now support 4 types: CGF, CGA, CHR, or SKIN.
- Extracted export.py functions to utils.py.
- Started adding new scene-based animation to replace AnimNode.
- Cleaned up UI.