python/paperwork-backend: init at 1.0.6

While not explicitly checked by setup.py or by the "chkdeps" command
from the project I have added pyinsane2 and pyocr to the list of
dependencies as well, because they're referenced in the source.

Tested by building against Python 3.3, 3.4, 3.5 and 3.6.

The build against Python 3.6 failed because pycairo doesn't build, so
it's a non-issue at least for paperwork-backend.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>