* Preview blend modes
No support for exporting and layer merging yet. Also need to fix the move tool preview.
* Preview blend modes on tile mode
* Raise layer limit to 1024
* Export images with layer blending modes
* Save blend modes in pxo files
* Merge layers with blending modes
* Fix crash when adding a new layer
* Preview blending in the other canvases
* Update DrawingAlgos.gd
* Move tool preview
* Re-arrange blend menu and add lighten, darken, linear burn and exclusion
* Add divide blend mode
* Add hue, saturation, color & luminosity blend modes
* Undo/redo when changing blend modes
