Parse vpi_user.h to extract all defines.  

Add those defines into simulator Namespace so they can be used from Python code (e.g., simulator.vpiNet)

The longer term plan for this is to expose the vpi_iterator/ vpi_scan methods so that any of the vpi* types can be scanned. 

Auto generating the VPI defines to load into the simulator Dictionary helps avoid any mismatch in the simulators with the IEEE standard.

I realise some of these are already in the local vpi_user.h - probably needs to be resolved?

Sending as a pull request but happy to discuss the idea further - this shows the general approach.