[IMP] Google or NymPy docstrings
[IMP] Google or NymPy docstrings

Allow [Google](http://sphinxcontrib-napoleon.readthedocs.org/en/latest/example_google.html)- or NymPy-style docstrings by adding the napoleon preprocessor
OCA/openupgradelib,hbrunn/openupgradelib,sebalix/openupgradelib,StefanRijnhart/openupgradelib,kurkop/openupgradelib