TBO TODO things:
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 * Undo/Redo tool. (hard)

 * Ask for size at export as png, pdf and svg. (easy)

 * Zoom levels: (easy)
    * fit to select, '3' key

 * Edit menu: (middle)
    * delete object

 * Import png/jpeg/gif/svg files to frame (middle)

 * Group objects in frame (hard)

 * Add doodle library: (easy)
    * arrows
    * more bubbles
    * more accesories
    * more doodle

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note: Difficult is right each TODO and could be:
    * hard: Require much time and knowlegde of how all program works.
    * middle: No require much time but require som knowledge of
              program.
    * easy: Only require basic C/GTK+/Cairo knowledge.