Fix examples

duniterpy/api/bma/api.py

duniterpy/api/bma/blockchain.py

duniterpy/api/bma/network.py

duniterpy/api/bma/node.py

examples/create_and_publish_identity.py

examples/create_public_key.py

examples/save_revoke_document.py

examples/send_certification.py

examples/send_membership.py

examples/send_transaction.py