- Unified "Zoom Rectangular" and "Zoom in" under one operation "Zoom In".
- Added zoom-out-rectangular equivalent for "Zoom Out".
- Animate zooming operation as a visual aid to how the function is transformed.
- Removed "Center Point" operation and replaced with translating the view via
  dragging (Google maps style).
- Made the zooming operations single shot and added the actions to the toolbar.

svn path=/trunk/KDE/kdeedu/kmplot/; revision=523534