* Implement 3D layers
* Remove unneeded files
* Fix bug where a single hidden layer would ignore all of the layers on top when exporting
* Fix pxo loading
* Remove junk nodes from 3DShapeEdit
Seems like they were created when I copied from the old 3D Options.tscn panel to the new 3D Shape Edit tool.
* Make light gizmos half the size, and hide gizmos when rotating
* Fix crash when using the 3D shape edit tool on a group layer
* Remove unneeded code in Canvas.gd
* Add torus in the Cel3DObject.Type enumerator
Torus isn't currently supported in Godot 3.5, but it is in 3.6 and 4.0, so this is just future-proofing. May break compatibility with .pxo files that were exported with 3D layers before this change.
* Toggle 3D object visibility
* Change texts and some variable names
* Fill translation strings
* Fix crash on group blending, and make the code in Export.blend_layers() more general
* Fix errors when attempting to draw on a 3D cel
Can occur when multiple cels are selected, some of them 3D and some of them pixel
* Make scene properties and objects be per-cel instead of per-layer
Breaks compatibility with previous .pxo files that had 3D layers. Also introduces serialize() and deserialize() methods to BaseCel
* Use if not layer is get_script() in GroupLayer.blend_children()
* Flip the condition in GroupLayer.blend_children()
* Fix bug where locked/invisible layers could get drawn
Regression from c2f6bf0f3f
* Move gizmo code to 3DShapeEdit's draw_start(), move some undo/redo logic to 3DShapeEdit
* Move all of the undo/redo code to 3DShapeEdit, simplify code in Cel3D
* Store Cel3D image data to pxo, for easy usage by external software
This makes importing projects with 3D layers to other software, such as Godot using godot_pixelorama_importer easier.
* Make the linter happy
* Fix bug where the previously selected object would remain selected when it got removed with undo
