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 ...
Don't forget to delete this before merge. You can always do `nosetests vispy/util/tests/test_meshdata.py` to only run a subset of tests.

Can you add some simple tests for the new types you added (cone/arrow)? Even just checking that they have the proper number of vertices given a few different `n_rows` or so would be a good start.