#160: Include examples into Python package

• Define functions in examples
• Allow to pass files path in f() prompt as arg
• Introduce __init__.py in examples which imports all examples
• Include examples folder into the Python package
• Document examples usage from Python interpreter
• Rework send-documents examples since urllib usage switch

Close #160 (closed).

examples/__init__.py

+"""
+Copyright  2014-2021 Vincent Texier <vit@free.fr>
+
+DuniterPy is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+DuniterPy is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+from .create_public_key import create_public_key
+from .listen_ws2p import listen_ws2p
+from .load_binary_encrypted_message import load_binary_encrypted_message
+from .load_binary_signed_message import load_binary_signed_message
+from .load_cleartext_ascii_armor_message import load_cleartext_ascii_armor_message
+from .load_credentials_file import load_credentials_file
+from .load_encrypted_ascii_armor_message import load_encrypted_ascii_armor_message
+from .load_local_blockchain import load_local_blockchain
+from .load_scuttlebutt_file import load_scuttlebutt_file
+from .request_available_nodes import request_available_nodes
+from .request_data import request_data
+from .request_data_async import request_data_async
+from .request_data_elasticsearch import request_data_elasticsearch
+from .request_data_graphql import request_data_graphql
+from .request_web_socket_block import request_web_socket_block
+from .request_ws2p import request_ws2p
+from .save_and_load_private_key_file import save_and_load_private_key_file
+from .save_and_load_private_key_file_ewif import save_and_load_private_key_file_ewif
+from .save_and_load_private_key_file_pubsec import save_and_load_private_key_file_pubsec
+from .save_and_load_private_key_file_wif import save_and_load_private_key_file_wif
+from .save_binary_encrypted_message import save_binary_encrypted_message
+from .save_binary_signed_message import save_binary_signed_message
+from .save_cleartext_ascii_armor_message import save_cleartext_ascii_armor_message
+from .save_encrypted_ascii_armor_message import save_encrypted_ascii_armor_message
+from .save_revoke_document import save_revoke_document
+from .send_certification import send_certification
+from .send_identity import send_identity
+from .send_membership import send_membership
+from .send_transaction import send_transaction