Using Cmake built-ins for SWIG

Created by: nhartland

So with this I can get the wrapper working and installing etc perfectly well. I'm sure it's messing with lots of good practice by installing to the python site_packages directly, and I'm probably messing up a lot of the cmake stuff (I don't know the first thing about cmake). But it does work (at least for me)!

No doubt it will not work on anybody else's machine.