Test and fix "pickleability" of Binary objects which has been recently broken while some cubes rely on this (eg fastimport). Do some licensing/pep8 cleanup along the way. Closes #13385274

usr/lib/python2*/*-packages/cubicweb/entities/
usr/lib/python2*/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/python2*/*-packages/cubicweb/*.py