add empty line before 'built with EasyBuild version X' line in easyconfig, fix debugging msg for extending MODULEPATH (was broken if skip was being used)

style cleanup for PythonPackage class and example easyconfigs for FFC, FIAT, Instant, Jinja2, ScientificPython, UFL, Viper

add example easyconfig for Sphinx (DOLFIN dependency), along for its dependencies Docutils, Jinja2 and setuptools