add after_shutdown hook

python/src/deltachat/hookspec.py

@@ -31,6 +31,10 @@ class PerAccount:
     def log_line(self, message):
         """ log a message related to the account. """
 
+    @account_hookspec
+    def after_shutdown(self):
+        """ Called when the account has been shutdown. """
+
     @account_hookspec
     def configure_completed(self, success):
         """ Called when a configure process completed. """