added updated versions of the old python tutorials

docs/conf.py

docs/datastructure.rst

docs/firststeps.rst

docs/garbagecollection.rst

docs/img/halfedge_structure.gif

docs/index.rst

docs/indexarrays.rst

docs/install.rst

docs/iterators.rst

docs/polymesh.rst

docs/properties.rst

docs/readwrite.rst

docs/trimesh.rst