[mod] Improve bma imports in send_*.py examples

examples/create_and_publish_identity.py

 import asyncio
 import getpass
 
-import duniterpy.api.bma as bma
+from duniterpy.api import bma
 from duniterpy.api.client import Client
 from duniterpy.documents import BlockUID, Identity
 from duniterpy.key import SigningKey

examples/save_revoke_document.py

@@ -4,7 +4,7 @@ import os
 import sys
 from typing import Optional
 
-import duniterpy.api.bma as bma
+from duniterpy.api import bma
 from duniterpy.api.client import Client
 from duniterpy.documents import Revocation, BlockUID, Identity
 from duniterpy.key import SigningKey

examples/send_certification.py

@@ -3,7 +3,7 @@ import asyncio
 import getpass
 from typing import Optional
 
-import duniterpy.api.bma as bma
+from duniterpy.api import bma
 from duniterpy.api.client import Client
 from duniterpy.documents import BlockUID, Identity, Certification
 from duniterpy.key import SigningKey

examples/send_membership.py

 import asyncio
 import getpass
 
-import duniterpy.api.bma as bma
+from duniterpy.api import bma
 from duniterpy.api.client import Client
 from duniterpy.documents import BlockUID, Identity, Membership
 from duniterpy.key import SigningKey