Made zooming related stuff more portable
Started reegineering Algorithm Visualizations to support zooming/panning

* Implemented some generic classes on the basis of the classes implemented for
  the GeometryEditor
* Ported the MonotonePieces visualization on that framework
* Some code needs still to be moved from MonotonePieces to general classes
* TriangulationPanel is instable at the moment due to unfinished changes