CMake find_package() module for PaGMO

Hi,

I've written a CMake module for PaGMO that makes use of a version file to auto-detect and link against the static library. I think this could be useful for others.

If there's anything unclear about the implementation, feel free to let me know.

Kind regards,

Kartik

Lines 74-78 cover the paths that will be searched to look for PaGMO. This list can be expanded to other common locations that people will install PaGMO to.