Update to fix some bugs

Changed:

1. Text added to the scene is now added as a floating selection, allowing you to move it with the selection tool before making the change permanent.

Fixed:

1. Text block creates memory leak in undo data.
2. Move tool doesn't have an undo action.
3. On restart, select Text tool, the preview shows the preview text Arial instead of the current selected font.
4. While selecting content if you press Ctrl+X, it leaves a solid line rect and copies nothing.
5. In the animation window if you copy a frame, it does not copy the frame duration.
6. If you create new document, draw, click close application without saving, it prompts to save file. Enter filename, prompts again and if you ignore the 2nd prompt, nothing has been written out.