Create view toolbar

This issue was created automatically from an original Mantis Issue. Further discussion may take place here.

The following buttons, which operate on the current window (and current dataset, when appropriate) should be implemented on a view toolbar: 1) reset center of rotation to the center of the current dataset 2) Reset the view to show everything visible 3) 'Back' in the current view stack 4) 'Forward' in the current view stack 5) (low priority) 'Save' current camera position (with name and thumbnail) 6) (low priority) Pulldown of saved camera positions.

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