Document how to reduce log4net verbosity.

Author: bgrainger

docs/UsingLog4netLogging.md

@@ -5,3 +5,13 @@ To integrate MySqlConnector with log4net, add the following line of code to your
 ```
 MySqlConnectorLogManager.Provider = new Log4netLoggerProvider();
 ```
+
+To reduce the verbosity of MySqlConnector logging, add the following element to your log4net config:
+
+```
+<log4net>
+  ...
+  <logger name="MySqlConnector">
+    <level value="WARN" />
+  </logger>
+```