Proxy Point Generator

First piece of the direct solver stuff.

Some bigger todos from my side:

• I wasn't quite sure where to put the file. Should I make a new folder for this?
• There are a lot of index and point arrays floating around and right now they're a bit of a mess between numpy.ndarray and pyopencl.array.Array. Is there some rule of thumb for what should be what? Is cl preferred?
• The proxy class does the following right now: generates proxy points, generates nearby neighbor points for each proxy ball and glue them all together in a big skeleton point array. I'm inclined to split the last two into separate functions. Thoughts?