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)
argpase instead of docopt
argparsing should work
releasing GIL fix #35
Executors: LinearSequenceExecutor (old behaviour), PhaseExecutor (specify phases to execute), ParallelExecutor
SWIG with thread does not work.

Other changes:

* executing sofa catches output
* change in exporter behaviour (exporter should not update the memory, just return an update)
* log.py is thread safe (maybe this helps markus)
Merge branch 'master' into executor_rework
Merge branch 'argparse' into executor_rework
Bunny works with phase and linearexecutor
simplified interface for defining exporters
Fixed bug in MiscMeshOperators (VTK 5 compatibility), please use the provided __SetInput functionality.
Patched simulation_runner to support new phase executor
fix #119
Merge remote-tracking branch 'origin/master'
unit test for c++