fix constants, update config example, add emc config validation

config_examples/config_full.example.json

@@ -175,22 +175,21 @@
         "password": "SuperSecurePassword",
         "ws_token": "secret_ws_t0ken."
     },
-    // The ExternalMessageConsumer config should only be enabled on an instance
-    // that listens to outside data from another instance. This should not be enabled
-    // in your producer of data.
     "external_message_consumer": {
         "enabled": false,
         "producers": [
           {
             "name": "default",
-            "url": "ws://localhost:8081/api/v1/message/ws",
+            "host": "127.0.0.2",
+            "port": 8080,
             "ws_token": "secret_ws_t0ken."
           }
         ],
-        "poll_timeout": 300,
+        "wait_timeout": 300,
         "ping_timeout": 10,
         "sleep_time": 10,
-        "remove_entry_exit_signals": false
+        "remove_entry_exit_signals": false,
+        "message_size_limit": 8
     },
     "bot_name": "freqtrade",
     "db_url": "sqlite:///tradesv3.sqlite",