meshdata.py and an example use it

Some change in meshdata.py
- Add cone and arrow mesh primitive
- add () in line 401 because it's a function
- modifie meshdata.vertices becaus they are a conflict with vertex_normal and face_normal call

Add an example to manipulate the mesh primitive 
- I have a problem with the primitive_mesh_viewer.Canvas.setData because this function doesn't change the camera view. Look in the code and help me please ...
Need docstring update here:
"If indexed is 'faces', then return (Nf, 3, 2) array of vertex indices with 3 edges per face, and two vertices per edge."