Added new subdivision surface operator (CGAL based):
http://doc.cgal.org/latest/Subdivision_method_3/index.html
Only Catmull-Clark Subdivision supported, for now.
Added a helper function to convert between vtkPolyData and CGAL Polyhedron without writing to disk.
Also added a new operator, using this helper function (vtk-File goes in, CGAL off-File goes out, hopefully)

Added option to switch subdivision method in subdivision surface operator(now supported: Catmull-Clark, Loop, DooSabin, sqrt3)
Fixed problem with vtk export. Now all four subdivision methods produce a valid vtk-file.
(Note: DooSabin and Catmull-Clark still do not produce a mesh containing only Tris! Catmull-Clark produces quads and DooSabin produces faces with more than four vertices)
Fixed Spelling of method DooSabin
Merge branch 'master' into new_subdivision_surface_operator
Created CGALPolyhedronToVTKPolyData_converter-Method.
Fixed wrong argument names in CGALOperators.h
Added new mesh simplification operator
(http://doc.cgal.org/latest/Surface_mesh_simplification/index.html#Chapter_Triangulated_Surface_Mesh_Simplification)
Merge branch 'master' of https://github.com/CognitionGuidedSurgery/msml into new_mesh_simplification_operator