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/dataimport/
usr/lib/python2*/*-packages/cubicweb/server/
usr/lib/python2*/*-packages/cubicweb/hooks/
usr/lib/python2*/*-packages/cubicweb/sobjects/
usr/lib/python2*/*-packages/cubicweb/schemas/
usr/share/cubicweb/migration/