* add a way to see indices
* fix some things
* Fixed more than one swatch selected if there is the same color available in an earlier swatch
* fixed wrong index drawn when moved to an smpty swatch
* make active_button public
* fixed wrong color getting stored in array (similar fix to #1108.)
* If the color selected in the palette is the same then it should take prioity.
* formatting
* hide 0 index
Fixes some issues with the Palettize effect where the output would be different if the palette size changed and empty swatches were added, even if the colors themselves stayed the same.
* Create a custom PixeloramaImage class, initial support for indexed mode
* Convert opened projects and images to indexed mode
* Use shaders for RGB to Indexed conversion and vice versa
* Add `is_indexed` variable in PixeloramaImage
* Basic undo/redo support for indexed mode when drawing
* Make image effects respect indexed mode
* Move code from image effects to ShaderImageEffect instead
* Bucket tool works with indexed mode
* Move and selection tools works with indexed mode
* Brushes respect indexed mode
* Add color_mode variable and some helper methods in Project
Replace hard-coded cases of Image.FORMAT_RGBA8 with `Project.get_image_format()` just in case we want to add more formats in the future
* Add a helper new_empty_image() method to Project
* Set new images to indexed if the project is indexed
* Change color modes from the Image menu
* Fix open image to replace cel
* Load/save indices in pxo files
* Merging layers works with indexed mode
* Layer effects respect indexed mode
* Add an `other_image` parameter to `PixeloramaImage.add_data_to_dictionary()`
* Scale image works with indexed mode
* Resizing works with indexed mode
* Fix non-shader rotation not working with indexed mode
* Minor refactor of PixeloramaImage's set_pixelv_custom()
* Make the text tool work with indexed mode
* Remove print from PixeloramaImage
* Rename "PixeloramaImage" to "ImageExtended"
* Add docstrings in ImageExtended
* Set color mode from the create new image dialog
* Update Translations.pot
* Show the color mode in the project properties dialog
