Adding WalkCow translated from walkCow.tcl

src/Cxx.md

src/Cxx/Rendering/CMakeLists.txt

src/Cxx/Rendering/WalkCow.cxx

src/Cxx/Rendering/WalkCow.md

src/Python.md

src/Python/Rendering/WalkCow.md

src/Python/Rendering/WalkCow.py