WIP - numpy based vector math; small wdb-wrapper fixes;

Hi Bryan,

I started creating some actual geometry using python-brlcad, but the result is not yet ready to be shown, will post as soon as I have nice examples.

There are however some additions I did regarding numpy based vector math which I want to share early, would be nice if you could review this pull request and tell me if this is going in the right direction...

All the vector math classes are WIP, I will add features as I need them. For now the biggest problem I have is that I don't know how to handle parenthesized combinations with libwdb (I mean those where the default precedence of the +, -, u operators needs to be overridden). The combinations/regions created with the current code only allow for the default precedence, which is suboptimal...

Thanks,
Csaba