[pdal] compile pdal with Python support

[Howard Butler]

> On Dec 1, 2015, at 5:41 AM, Luca Delucchi <lucadeluge at gmail.com> wrote:
> 
> Now the problem is to add python folder in the build instructions, I
> opened a ticket for this
> https://github.com/PDAL/PDAL/issues/1055

I always found this behavior of GDAL rather frustrating and hard to control. If you're using Python inside of a virtual environment or something, it's difficult to know at cmake time where to install things. You end up manually installing anyway. That's why the "use PDAL from Python" code is just an extension that can be easy_install'd at the moment.

Howard