First option is to affect the selected pixels only. The second it to affect the current cel, or the entire frame (all cels of the frame). Options to affect all frames and all projects will be added next. I also made changes to Canvas.handle_undo() and handle_redo() to make this work.
Once all these options are added successfully in HSVDialog, they will also be added in the rest of the Image effect dialogs.
A Project class contains project-specific data like name, undo_redo, frames, layers, tags and brushes. These variables have been moved from Global. This is the first step towards multiple tab support, where each tab will be a different Project.
Moved code from Global.gd and Canvas.gd to DrawingAlgos.gd. Will also move the fill_gaps and draw_brush methods of Canvas.gd next. Maybe even refactor the inside of them a bit to make them easier to read.
