improve wallet usage help (#794)

neo/Prompt/CommandBase.py

@@ -125,12 +125,15 @@ def __command_with_parents(self):
             s = self.__parent_command.__command_with_parents() + " " + s
         return s
 
+    def _usage_str(self):
+        return f"Usage: {self.__command_with_parents()} COMMAND"
+
     def handle_help(self, arguments):
         item = get_arg(arguments)
         if item == 'help':
             if len(self.__sub_commands) > 0:
                 # show overview of subcommands and their purpose
-                print(f"\nUsage: {self.__command_with_parents()} COMMAND\n")
+                print(f"\n{self._usage_str()}\n")
                 print(f"{self.command_desc().short_help.capitalize()}\n")
                 print("Commands:")
 

neo/Prompt/Commands/Wallet.py

@@ -70,6 +70,10 @@ def execute(self, arguments):
             print(f"{item} is an invalid parameter")
             return
 
+    def _usage_str(self):
+        base = super()._usage_str()
+        return base + " (or \"wallet\" to show the wallet contents)"
+
 
 class CommandWalletCreate(CommandBase):