Colors!

- Save colors to letter keys using Ctrl+Letter.
- Finish zooming and panning.
- Speed up intro animation.
- Sort out idle vs paint priority issue.
+ Toolbar repaint issue.
+ Get tutorial paintings from Scott Nash.
+ Improve opacity and size scrollbar behavior: click to set.  Maybe a custom widget?
+ Implement pickup color tool.
+ Add FPS counter.
+ Optimize framerate.
+ Improve videopaint
 + Use Nirav's pygame extension.
 + Calibration button.
+ Test Journal save & resume.
+ Fix cursor drawing.
+ Implement Copy & Paste.
+ Implement joypad key bindings.
+ Implement stylus support using evtest.
+ Speed up painting performance of large brushes.
+ Single stroke quick undo.
+ Button to adjust playback speed.
- Implement Wacom support.
- Fullscreen button.
+ Confirm image clear.
- Ignore painting while playing back.  Make them pause first!
+ Copy should create a new 1x gdk.Image.