Creating a Mesh object while there is no OpenGl context raises an error

```
We have an app that sometimes crashes if a visualizatio containing a Mesh is 
shown too soon. The error lies in the Shader that is created in the 
Mesh.__init__. 

Maybe we can delay the creation of the shader (lazy programming) or do 
something similar in the Shader object.
```

Original issue reported on code.google.com by `almar.klein@gmail.com` on 15 Aug 2012 at 3:05
