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 ...
This comment appears to be incorrect. Later in the code this is initialized as:
```
np.empty((verts.shape[0], 3, 2), dtype=np.uint)
```