Introduce a `pagmo2WithPython` which overrides the pagmo2 expression
and enables the pygmo build. Then hand it over to `buildPythonPackage`
by making it the src to produce a usable package.
- python 2.7, 3+
- skipping tests becuase none are easy to run (require some parallel workers)
- fetchFromgitHub so that running tests in future is possible
