ecCodes Python bindings

In order to enable the Python bindings in the build,
use the -DENABLE_PYTHON=ON in the cmake step:

  cmake /path/to/src -DENABLE_PYTHON=ON

This will enable the build of the Python bindings with 
NumPy support enabled. Python needs to be in the path
and, of course, the NumPy package installed.

On 'make install', the Python bindings will be installed under
'${ecCodes_install_dir}/lib/pythonX.X/site-packages/eccodes',
where X.X is the version of python used to build the bindings.
Add this folder to your PYTHONPATH and you are ready to go.
